FREEMEDSITE MRCS ACADEMY • ARTICLE 14 • PAPER 1 SURGICAL ANATOMY

Lower Limb Surgical Anatomy Made Easy for MRCS Part A

Understand gluteal muscles, hip neurovascular risks, femoral triangle, sciatic and fibular nerves, knee, popliteal fossa, ankle and foot in a clear clinical sequence. Then practise 40 original five-option single best answer questions.

12 teaching modules52 saved revision topics40 explained A–E SBAs3 original schematic diagrams

FreeMedSite education • 16 October 2026 • Original practice, not official MRCS examination questions

How to use this chapter

Study one region, describe the important nerve and vessel relationships aloud, tick the related objective and answer the applied SBAs. Each answer explains all four distractors. Checklist and quiz progress are stored only in your current browser.

For clinical trauma, neurological and vascular assessment, follow up-to-date local protocols. Educational anatomy is not a substitute for emergency decision support.

On this page

Gluteal musclesHip joint capsule, circulationFemoral triangle, sheathAnteriorPosterior thigh, sciatic nerveKnee ligaments, menisciPopliteal fossaLeg compartments, tibialDistal sensory territoriesAnkle ligamentsFoot arches, plantar nervesArterialRevision checklist40 SBAsFrequently asked questionsReferences & next lessons

1. Gluteal muscles and hip abductor mechanics

Gluteus medius and minimus stabilise the pelvis during single-leg stance. They receive the superior gluteal nerve (L4–S1), which also innervates tensor fasciae latae. Gluteus maximus is the major powerful hip extensor and is supplied by the inferior gluteal nerve (L5–S2). Deep rotators help external rotation and posterior stability.

Applied anatomy

If the right abductors fail, the pelvis drops on the LEFT when the patient stands on the RIGHT; the patient may lean the trunk right to compensate. A superior gluteal injury can occur during pelvic surgery or trauma. Separate true Trendelenburg weakness from pain-limited stance.

Exam pearl

Stance side is the weak side; pelvic drop is contralateral.

2. Hip joint capsule, circulation and surgical risk

The femoral head and acetabulum form a ball-and-socket joint. The iliofemoral ligament is a strong anterior restraint to hyperextension; the posterior capsule and short rotators protect posterior stability. Adult femoral-head perfusion depends mainly on superior retinacular branches of medial circumflex femoral artery; displaced intracapsular neck fractures can disrupt these vessels.

Applied anatomy

Posterior dislocation and posterior hip surgical exposures risk sciatic nerve stretch or trauma. Document dorsiflexion, plantarflexion, foot sensation and pulses before and after a hip reduction. During posterior arthroplasty the posterior capsule and external rotators are often repaired to reduce dislocation risk.

Exam pearl

Medial circumflex femoral retinacular vessels matter most for adult head viability.

3. Femoral triangle, sheath and landmarks

The superior border is the inguinal ligament; sartorius forms the lateral border, adductor longus the medial border. The floor contains iliopsoas laterally and pectineus medially. The contents run lateral to medial: Nerve, Artery, Vein, Empty femoral canal, Lymphatics (NAVEL). Importantly, femoral nerve is OUTSIDE the femoral sheath, whereas artery, vein and canal are inside.

Applied anatomy

The femoral pulse lies near the mid-inguinal point (ASIS to pubic symphysis midpoint), not the exact midpoint of the inguinal ligament (ASIS to pubic tubercle). For femoral venous access, remember femoral vein is medial to artery in the proximal thigh. Femoral nerve palsy impairs knee extension and patellar reflex.

Exam pearl

Femoral nerve is lateral to artery but outside the sheath.

4. Anterior and medial thigh compartments

Femoral nerve (L2–L4) supplies quadriceps and much anterior thigh; its sensory saphenous branch runs through adductor canal toward medial leg and foot. Obturator nerve (L2–L4) supplies most thigh adductors, entering via obturator canal. Adductor magnus is divided functionally: adductor portion supplied by obturator nerve, hamstring portion by tibial sciatic division.

Applied anatomy

The adductor canal is a fascial passage deep to sartorius carrying femoral vessels, saphenous nerve and nerve to vastus medialis. Femoral artery passes through the adductor hiatus to become popliteal artery. Knee extension deficit suggests femoral neuropathy; isolated adduction deficit suggests obturator dysfunction.

Exam pearl

Saphenous nerve is sensory; do not attribute quadriceps paralysis to isolated saphenous injury.

5. Posterior thigh, sciatic nerve and hamstrings

Sciatic nerve is formed from L4–S3 sacral plexus and typically leaves pelvis through greater sciatic foramen below piriformis. Its tibial and common fibular divisions often travel within one sheath until separating above popliteal fossa. Tibial division supplies most hamstring muscles; short head of biceps femoris is supplied by common fibular division.

Applied anatomy

Posterior hip dislocations are associated with sciatic injury, especially the fibular division. Posterior hip surgery requires protection from retraction, traction and extreme hip positioning. Compare ankle dorsiflexion AND plantarflexion to distinguish a broader sciatic lesion from isolated fibular palsy.

Exam pearl

Short head of biceps femoris is the hamstring-region fibular-division exception.

6. Knee ligaments, menisci and stabilisation

The ACL is a primary restraint to anterior tibial translation and helps rotational stability; PCL prevents posterior translation. Medial collateral ligament resists valgus stress; lateral collateral and posterolateral structures resist varus/external rotation. Peripheral meniscus (red–red region) is relatively vascular; central white–white zone has limited intrinsic healing.

Applied anatomy

Lachman testing assesses ACL laxity near 20–30 degrees flexion, posterior drawer assesses PCL. Clinical decisions require symptoms, instability, concomitant injury and imaging rather than single test alone. A meniscal tear may be reparable depending on vascular zone, morphology and stability.

Exam pearl

ACL anterior; PCL posterior; meniscal peripheral rim vascular.

7. Popliteal fossa and knee dislocation vascular assessment

The popliteal fossa is bordered superiorly by biceps femoris and semimembranosus/semitendinosus; inferiorly by medial and lateral gastrocnemius heads. Its central neurovascular bundle lies superficial to deep: tibial NERVE, popliteal VEIN, popliteal ARTERY (N–V–A). Popliteal artery lies deepest against posterior knee and is relatively tethered.

Applied anatomy

Knee dislocation can produce popliteal arterial intimal damage even when the foot is warm and pulses are palpated. Follow local protocols for vascular examination, ankle–brachial indices where applicable, repeat examinations and urgent vascular imaging/consultation when indicated. Never use a single pulse check to exclude injury.

Exam pearl

Popliteal N–V–A and persistent concern after knee dislocation despite pulses.

8. Leg compartments, tibial and fibular nerves

Anterior leg compartment (deep fibular nerve) dorsiflexes ankle and extends toes; lateral compartment (superficial fibular nerve) everts foot. Superficial posterior compartment contains gastrocnemius, soleus and plantaris; deep posterior compartment contains tibialis posterior and long toe flexors with tibial nerve and posterior tibial vessels. Posterior compartments are tibial-nerve innervated.

Applied anatomy

Common fibular nerve winds around fibular neck and may be compressed by fracture or tight plaster. Combined dorsiflexion/eversion loss suggests common fibular lesion, whereas deep branch injury can spare eversion. Acute compartment syndrome is a clinical emergency; palpable pulses do not exclude it.

Exam pearl

Anterior = deep fibular; lateral = superficial fibular; posterior = tibial.

9. Distal sensory territories and foot drop localisation

Deep fibular nerve supplies first dorsal web space, while superficial fibular supplies most dorsal foot. Sural nerve supplies lateral foot border, and saphenous nerve supplies medial leg and medial foot. Plantar skin is mostly supplied by tibial-derived plantar nerves. These small clear zones are more useful than memorising broad overlapping cutaneous maps.

Applied anatomy

Foot drop may arise from common fibular neuropathy, sciatic neuropathy or L5 radiculopathy. Weak tibialis posterior inversion (tibial nerve, largely L5) or hip abduction favours a more proximal lesion than isolated common fibular nerve entrapment; electrodiagnostics and imaging are tailored to clinical findings.

Exam pearl

First web deep fibular; medial leg saphenous; lateral foot sural.

10. Ankle ligaments and extensor/flexor retinacula

ATFL is frequently injured by inversion in plantarflexion; CFL resists inversion particularly near neutral ankle position. Syndesmotic ligaments are threatened by rotational high-ankle mechanisms. The tarsal tunnel runs posterior to medial malleolus beneath flexor retinaculum: tibialis posterior, flexor digitorum longus, posterior tibial vessels, tibial nerve, flexor hallucis longus.

Applied anatomy

Tarsal tunnel compression produces plantar paraesthesia; deep fibular entrapment at anterior ankle produces dorsal first web-space symptoms. Posterior tibial pulse is found behind medial malleolus, while dorsalis pedis is generally lateral to extensor hallucis longus tendon.

Exam pearl

Tom, Dick, And Very Nervous Harry (tunnel sequence) and ATFL inversion/plantarflexion.

11. Foot arches, plantar nerves and tendon insertions

Plantar fascia attaches proximally near the medial calcaneal tubercle and contributes to the windlass mechanism as toes dorsiflex. Tibialis posterior is a dynamic medial arch supporter; fibularis longus runs behind the lateral malleolus beneath cuboid toward the first ray, supporting transverse arch. Tibial nerve divides into medial and lateral plantar nerves.

Applied anatomy

Medial plantar nerve supplies medial 3.5 plantar toes and several intrinsic muscles; lateral plantar supplies the rest of sole/toes and many intrinsic muscles. Plantar heel tenderness alone differs from burning plantar neuropathic pain. Sensory distributions overlap and should not substitute for a full examination.

Exam pearl

Fibularis longus crosses beneath cuboid; tibialis posterior supports medial arch.

12. Arterial and venous surface anatomy

External iliac artery continues as femoral artery below inguinal ligament; profunda femoris supplies deep thigh and circumflex vessels. Femoral artery becomes popliteal after adductor hiatus; popliteal divides into anterior tibial and tibioperoneal trunk, leading to posterior tibial and fibular arteries. Anterior tibial continues as dorsalis pedis. Great saphenous vein passes anterior to medial malleolus; small saphenous passes posterior to lateral malleolus.

Applied anatomy

In high-energy limb injury document both dorsalis pedis and posterior tibial pulses, capillary refill, temperature, motor and sensory function, and changes over time. If clinical vascular compromise is suspected, expedite specialist assessment rather than relying on one normal sign.

Exam pearl

Femoral → popliteal after adductor hiatus; great saphenous medial, small saphenous lateral.

52-topic interactive revision checklist

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Hip and gluteal mechanics

Superior vs inferior gluteal innervation Gluteus medius/minimus pelvic stabilisation Trendelenburg positive-side interpretation Sciatic nerve and piriformis relationship Hip ligament and capsular stability Inferior gluteal gluteus maximus action

Hip perfusion and nerve risk

Medial circumflex retinacular vessels Ligamentum teres variable supply Intracapsular neck fracture AVN risk Posterior hip sciatic assessment Posterior hip surgical sciatic protection

Femoral triangle and thigh

Triangle borders and floor NAVEL contents and femoral sheath exception Mid-inguinal point vs ligament midpoint Femoral nerve roots and patellar reflex Obturator nerve/adductor functions Adductor magnus dual innervation Femoral sheath artery/vein/canal order

Adductor canal and posterior thigh

Saphenous sensory territory Adductor hiatus and popliteal transition Sciatic L4–S3 roots Short head biceps femoris nerve Hamstring tibial division Popliteal fossa boundary muscles

Knee and popliteal region

ACL anterior tibial translation PCL posterior tibial translation MCL/LCL collateral functions Meniscus red–red vs white–white zones Popliteal superficial-to-deep N–V–A Popliteal injury despite palpable pulse Popliteus knee unlocking

Leg compartments and fibular nerves

Four leg compartments Deep fibular motor functions Superficial fibular motor functions Common fibular neck injury deficits First dorsal web-space sensation Tibial motor/sole sensory function Sural vs saphenous sensory territory

Ankle, tarsal tunnel and foot

Medial tarsal tunnel sequence ATFL and CFL distinction Tarsal tunnel symptoms Medial/lateral plantar nerves Tibialis posterior arch support Fibularis longus cuboid pathway Plantar fascia windlass mechanism

Vessels and advanced localisation

Femoral/profunda artery relations Dorsalis pedis pulse landmark Posterior tibial pulse landmark Great vs small saphenous ankle course Foot drop L5 vs fibular localising signs Achilles S1 vs knee L3/L4 reflex Great saphenous vs small saphenous vein anatomy

40 original MRCS-style clinical SBAs

Five options per question; exactly one best answer. Explanations address every distractor separately, followed by an exam pearl, examiner trap and answered viva extension. Correct answer positions are distributed evenly across A–E.

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Question 1 of 40

Question 1 of 40 • Gluteus medius

Q01. Following pelvic trauma, a patient stands on the right leg and the left side of the pelvis drops. Which nerve is most likely injured?

A. Right superior gluteal nerve B. Right inferior gluteal nerve C. Left femoral nerve D. Right obturator nerve E. Left sciatic nerve

View detailed explanation, examiner trap and viva

Correct answer: A. Right superior gluteal nerve.

Why correct: A right superior gluteal lesion weakens right gluteus medius and minimus, so the unsupported left hemipelvis falls during right single-leg stance.

Why the other options are incorrect:

B. Right inferior gluteal nerve: Supplies gluteus maximus and particularly affects powerful hip extension.

C. Left femoral nerve: Causes quadriceps weakness on the left, not right stance-side pelvic drop.

D. Right obturator nerve: Supplies thigh adductors rather than principal pelvic stabilising abductors.

E. Left sciatic nerve: Causes posterior thigh and distal limb abnormalities, not this isolated right hip-abductor deficit.

Exam pearl: Pelvic drop is on the opposite side to the weak stance-side abductors.

Examiner trap: Differentiate the side of pelvic drop from the side of nerve injury.

Viva extension — Which muscles are primarily supplied by the superior gluteal nerve?
Answer: Gluteus medius, gluteus minimus and tensor fasciae latae.

Question 2 of 40 • Hip surgery sciatic nerve

Q02. A patient develops weakness of ankle dorsiflexion and plantarflexion after a posterior hip operation. Which major nerve is most at risk?

A. Femoral nerve B. Sciatic nerve C. Obturator nerve D. Superior gluteal nerve E. Lateral femoral cutaneous nerve

View detailed explanation, examiner trap and viva

Correct answer: B. Sciatic nerve.

Why correct: The sciatic nerve runs posterior to the hip and is a key structure at risk from retractors, dissection and traction in posterior approaches.

Why the other options are incorrect:

A. Femoral nerve: Courses anterior to the hip and principally supplies hip flexion and knee extension.

C. Obturator nerve: Supplies medial-thigh adductors rather than most distal leg muscles.

D. Superior gluteal nerve: Injury causes hip-abductor dysfunction and Trendelenburg gait.

E. Lateral femoral cutaneous nerve: Is sensory to the lateral thigh and does not cause widespread distal weakness.

Exam pearl: Posterior hip surgery: assess sciatic function before and after operation.

Examiner trap: A sciatic lesion can resemble common fibular palsy but may also weaken plantarflexion.

Viva extension — Which sciatic division is frequently more vulnerable?
Answer: The common fibular division is often particularly susceptible to traction.

Question 3 of 40 • Femoral triangle boundaries

Q03. A surgeon exposes the femoral triangle. Which structure forms its superior boundary?

A. Sartorius B. Adductor longus C. Inguinal ligament D. Pectineus E. Iliopsoas

View detailed explanation, examiner trap and viva

Correct answer: C. Inguinal ligament.

Why correct: The inguinal ligament forms the triangle roof-like superior border; sartorius is lateral and adductor longus medial, with iliopsoas and pectineus contributing to the floor.

Why the other options are incorrect:

A. Sartorius: Forms the lateral boundary rather than superior boundary.

B. Adductor longus: Forms the medial boundary.

D. Pectineus: Contributes to the floor of the triangle.

E. Iliopsoas: Contributes to the floor, not the superior margin.

Exam pearl: Femoral triangle: inguinal above, sartorius lateral, adductor longus medial.

Examiner trap: Do not confuse triangle boundaries with its floor.

Viva extension — What is the lateral-to-medial order of its main neurovascular contents?
Answer: Femoral nerve, artery, vein and canal or lymphatics.

Question 4 of 40 • Femoral sheath

Q04. During a femoral vascular exposure, which structure lies lateral to the femoral artery but outside the femoral sheath?

A. Femoral vein B. Femoral canal C. Deep inguinal lymphatics D. Femoral nerve E. Femoral branch of genitofemoral nerve

View detailed explanation, examiner trap and viva

Correct answer: D. Femoral nerve.

Why correct: The femoral nerve enters the thigh lateral to the artery beneath the inguinal ligament and is not within the femoral sheath.

Why the other options are incorrect:

A. Femoral vein: Lies medial to the artery within the femoral sheath.

B. Femoral canal: Lies medial to the vein inside the medial compartment of the sheath.

C. Deep inguinal lymphatics: Occupy the medial canal rather than lying lateral to the artery.

E. Femoral branch of genitofemoral nerve: Supplies skin of the femoral triangle and is not the large lateral motor nerve asked about.

Exam pearl: NAVEL is order, but the nerve is outside the femoral sheath.

Examiner trap: Femoral triangle and femoral sheath are not synonymous compartments.

Viva extension — Which fascial spaces form the femoral sheath?
Answer: Lateral arterial, intermediate venous and medial femoral-canal compartments.

Question 5 of 40 • Femoral nerve dysfunction

Q05. After a retroperitoneal haematoma, a patient cannot actively extend the knee and has a reduced patellar reflex. Which nerve is implicated?

A. Obturator nerve B. Sciatic nerve C. Superior gluteal nerve D. Tibial nerve E. Femoral nerve (L2–L4)

View detailed explanation, examiner trap and viva

Correct answer: E. Femoral nerve (L2–L4).

Why correct: Femoral nerve supplies quadriceps, which extends the knee, and forms the efferent component of the patellar reflex.

Why the other options are incorrect:

A. Obturator nerve: Mainly supplies thigh adduction rather than quadriceps.

B. Sciatic nerve: Supplies hamstrings and most leg/foot innervation via its divisions.

C. Superior gluteal nerve: Supplies primary hip abductors.

D. Tibial nerve: Supplies posterior leg plantarflexors and plantar foot sensation.

Exam pearl: Quadriceps weakness plus lost knee jerk points to femoral nerve or L3–L4 pathway.

Examiner trap: A root lesion can mimic femoral neuropathy; check hip adduction and paraspinal findings.

Viva extension — Which cutaneous branch continues to the medial leg?
Answer: Saphenous nerve.

Question 6 of 40 • Adductor canal

Q06. A patient receives an adductor canal block for knee surgery. Which sensory nerve travels through the canal and supplies the medial leg?

A. Saphenous nerve B. Sural nerve C. Common fibular nerve D. Deep fibular nerve E. Lateral femoral cutaneous nerve

View detailed explanation, examiner trap and viva

Correct answer: A. Saphenous nerve.

Why correct: The saphenous nerve is the terminal sensory branch of the femoral nerve and travels in the adductor canal before emerging to supply medial leg and foot.

Why the other options are incorrect:

B. Sural nerve: Supplies posterolateral leg and lateral foot.

C. Common fibular nerve: Runs near the fibular neck, not along the canal.

D. Deep fibular nerve: Supplies the anterior leg compartment and first web-space sensation.

E. Lateral femoral cutaneous nerve: Supplies lateral-thigh skin, not medial leg.

Exam pearl: Saphenous = medial leg sensory, no motor supply.

Examiner trap: A saphenous neuropathy alone cannot paralyse knee extension.

Viva extension — Which artery accompanies it within the canal?
Answer: Femoral artery (with femoral vein).

Question 7 of 40 • Obturator nerve

Q07. A patient sustains a pelvic fracture and has marked weakness when bringing the thighs together. Which nerve is most likely injured?

A. Femoral nerve B. Obturator nerve (L2–L4) C. Superior gluteal nerve D. Tibial nerve E. Common fibular nerve

View detailed explanation, examiner trap and viva

Correct answer: B. Obturator nerve (L2–L4).

Why correct: The obturator nerve traverses the obturator canal and supplies most medial thigh adductors, explaining impaired hip adduction.

Why the other options are incorrect:

A. Femoral nerve: Primarily innervates anterior thigh quadriceps and iliacus.

C. Superior gluteal nerve: Supplies hip abductors and tensor fasciae latae.

D. Tibial nerve: Supplies posterior leg and plantar intrinsic muscles.

E. Common fibular nerve: Supplies anterior/lateral leg through its branches, producing dorsiflexion or eversion deficits.

Exam pearl: Obturator neuropathy = adduction weakness, possible medial thigh sensory change.

Examiner trap: Adductor magnus has dual innervation: adductor part obturator, hamstring part tibial sciatic.

Viva extension — Which opening transmits the obturator nerve into the thigh?
Answer: Obturator canal.

Question 8 of 40 • Femoral head circulation

Q08. A displaced intracapsular femoral neck fracture threatens the principal adult blood supply to the femoral head. Which vessel provides most retinacular flow?

A. Artery of ligamentum teres alone B. Inferior epigastric artery C. Medial circumflex femoral artery D. Superficial circumflex iliac artery E. Anterior tibial artery

View detailed explanation, examiner trap and viva

Correct answer: C. Medial circumflex femoral artery.

Why correct: Deep branches of the medial circumflex femoral artery give retinacular vessels that supply much of the adult femoral head, explaining osteonecrosis risk.

Why the other options are incorrect:

A. Artery of ligamentum teres alone: Contributes variably but is not the dominant adult supply.

B. Inferior epigastric artery: Supplies abdominal wall rather than femoral head.

D. Superficial circumflex iliac artery: Is a superficial groin vessel, not principal retinacular inflow.

E. Anterior tibial artery: Supplies the anterior leg and foot, not hip epiphysis.

Exam pearl: Medial circumflex femoral retinacular branches matter in intracapsular fractures.

Examiner trap: The ligamentum teres artery should not be assumed sufficient in adults.

Viva extension — How does the fracture level affect this risk?
Answer: Displaced intracapsular fractures may disrupt retinacular vessels more than extracapsular fractures.

Question 9 of 40 • Gluteal injection

Q09. Why is a properly identified superolateral gluteal injection region preferred over the inferomedial buttock?

A. It avoids the femoral triangle artery B. It protects the femoral nerve in the sheath C. It prevents all injury to superior gluteal vessels D. It reduces the risk of sciatic nerve injury E. It avoids the tarsal tunnel

View detailed explanation, examiner trap and viva

Correct answer: D. It reduces the risk of sciatic nerve injury.

Why correct: The sciatic nerve courses deep in the inferior/medial gluteal region; safe site selection reduces risk of direct injection trauma.

Why the other options are incorrect:

A. It avoids the femoral triangle artery: The femoral artery is anterior in the groin, not the chief buttock hazard.

B. It protects the femoral nerve in the sheath: The femoral nerve passes under the inguinal ligament anteriorly.

C. It prevents all injury to superior gluteal vessels: Technique reduces risks but does not guarantee zero vascular injury.

E. It avoids the tarsal tunnel: The tarsal tunnel is at the medial ankle, unrelated to buttock injections.

Exam pearl: Identify landmarks meticulously; ventrogluteal injection sites are often preferred in practice.

Examiner trap: The reason is avoiding sciatic nerve, not an artery in the femoral triangle.

Viva extension — Which pelvic exit does the sciatic nerve usually use?
Answer: Greater sciatic foramen inferior to piriformis.

Question 10 of 40 • Hamstring innervation

Q10. A posterior-thigh nerve lesion selectively weakens the short head of biceps femoris but spares most other hamstrings. Which nerve division is likely affected?

A. Femoral nerve B. Obturator nerve C. Superior gluteal nerve D. Pudendal nerve E. Common fibular division of sciatic nerve

View detailed explanation, examiner trap and viva

Correct answer: E. Common fibular division of sciatic nerve.

Why correct: The short head of biceps femoris is supplied by the common fibular component of the sciatic nerve, unlike most true hamstrings supplied by the tibial component.

Why the other options are incorrect:

A. Femoral nerve: Innervates anterior thigh rather than the short head of biceps femoris.

B. Obturator nerve: Chiefly innervates thigh adductors.

C. Superior gluteal nerve: Innervates hip abductors.

D. Pudendal nerve: Supplies perineal musculature and sensation, not thigh hamstrings.

Exam pearl: Short head of biceps femoris is the classic hamstring-region fibular-division exception.

Examiner trap: Not every muscle in the posterior thigh has tibial-division innervation.

Viva extension — What innervates semitendinosus?
Answer: Tibial division of the sciatic nerve.

Question 11 of 40 • Popliteal fossa depth

Q11. During exploration of a popliteal aneurysm, what is the correct superficial-to-deep order of the central neurovascular bundle?

A. Tibial nerve, popliteal vein, popliteal artery B. Popliteal artery, vein, tibial nerve C. Femoral nerve, artery, vein D. Popliteal vein, artery, sciatic nerve E. Common fibular nerve, femoral vein, femoral artery

View detailed explanation, examiner trap and viva

Correct answer: A. Tibial nerve, popliteal vein, popliteal artery.

Why correct: Within the fossa the tibial nerve is generally most superficial, the popliteal vein intermediate and the artery deepest against the capsule/femur.

Why the other options are incorrect:

B. Popliteal artery, vein, tibial nerve: This reverses the characteristic depth relationship.

C. Femoral nerve, artery, vein: Those lie in the anterior thigh/femoral triangle, not fossa.

D. Popliteal vein, artery, sciatic nerve: The nerve is not normally deepest and sciatic usually divides more proximally.

E. Common fibular nerve, femoral vein, femoral artery: Femoral vessels are proximal and common fibular tracks laterally.

Exam pearl: Popliteal N–V–A superficial to deep.

Examiner trap: The artery lies deepest and is vulnerable in knee dislocation.

Viva extension — Why might popliteal aneurysm produce nerve symptoms?
Answer: Expansion compresses adjacent tibial nerve and other fossa structures.

Question 12 of 40 • Knee dislocation arterial risk

Q12. A patient with a reduced posterior knee dislocation has a warm foot and palpable pulses. Which vessel remains particularly at risk from the injury?

A. Femoral profunda artery B. Popliteal artery C. External iliac artery D. Dorsalis pedis artery E. Superior gluteal artery

View detailed explanation, examiner trap and viva

Correct answer: B. Popliteal artery.

Why correct: The popliteal artery is tethered proximally and distally and can sustain intimal injury even when distal pulses persist; urgent structured vascular assessment is necessary.

Why the other options are incorrect:

A. Femoral profunda artery: Located proximally in deep thigh, not across the injured knee.

C. External iliac artery: Lies in pelvis above inguinal ligament.

D. Dorsalis pedis artery: Distal pulse location; its presence does not exclude proximal intimal injury.

E. Superior gluteal artery: Supplies gluteal musculature, not knee vascular conduit.

Exam pearl: Palpable pulses do not by themselves exclude popliteal vascular injury.

Examiner trap: Ankle–brachial index and serial exams follow institutional knee-dislocation vascular protocols.

Viva extension — What mechanism can produce delayed ischaemia?
Answer: Popliteal arterial intimal injury with subsequent thrombosis.

Question 13 of 40 • ACL anatomy

Q13. A footballer tears the anterior cruciate ligament. Which tibial movement relative to the femur is primarily restrained by the ACL?

A. Posterior translation B. Isolated valgus opening C. Anterior translation D. Isolated varus opening E. Patellar lateral glide only

View detailed explanation, examiner trap and viva

Correct answer: C. Anterior translation.

Why correct: The ACL is the major restraint to anterior tibial translation and helps control rotational stability, particularly near knee extension.

Why the other options are incorrect:

A. Posterior translation: Primarily resisted by the PCL.

B. Isolated valgus opening: The MCL is the main medial valgus restraint.

D. Isolated varus opening: The LCL and posterolateral corner are major restraints.

E. Patellar lateral glide only: Patellar stabilisers include medial patellofemoral soft tissues, not ACL.

Exam pearl: ACL checks anterior tibial drawer and pivoting instability.

Examiner trap: Lachman evaluates anterior translation near 20–30 degrees flexion.

Viva extension — Which ligament checks posterior translation?
Answer: Posterior cruciate ligament.

Question 14 of 40 • Meniscus vascular zone

Q14. Which portion of an adult meniscus has the best intrinsic healing potential after repair?

A. Inner white–white zone B. Central avascular free edge C. Articular cartilage alone D. Peripheral red–red zone E. Intercondylar notch synovium

View detailed explanation, examiner trap and viva

Correct answer: D. Peripheral red–red zone.

Why correct: The vascularised peripheral rim receives capsular genicular branches, whereas inner white–white regions are poorly vascularised and have limited healing.

Why the other options are incorrect:

A. Inner white–white zone: Has sparse blood supply and poorer intrinsic healing.

B. Central avascular free edge: Has minimal vascular connection.

C. Articular cartilage alone: Is distinct tissue from fibrocartilaginous meniscus.

E. Intercondylar notch synovium: Not a meniscal vascular zone.

Exam pearl: Peripheral meniscal tears are more likely to heal than central avascular tears.

Examiner trap: Healing depends on tear pattern, stability, tissue and patient factors too.

Viva extension — What are the three descriptive vascular zones?
Answer: Red–red, red–white and white–white.

Question 15 of 40 • Common fibular nerve at neck

Q15. Following a fibular-neck fracture, the patient cannot dorsiflex or evert the foot. Which nerve is most likely injured?

A. Isolated deep fibular nerve B. Isolated superficial fibular nerve C. Tibial nerve D. Saphenous nerve E. Common fibular nerve

View detailed explanation, examiner trap and viva

Correct answer: E. Common fibular nerve.

Why correct: At the fibular neck the common fibular nerve is superficial; injury affects both deep branch dorsiflexors and superficial branch evertors.

Why the other options are incorrect:

A. Isolated deep fibular nerve: Would mainly impair dorsiflexion while eversion can be maintained.

B. Isolated superficial fibular nerve: Weakens eversion but generally spares tibialis anterior dorsiflexion.

C. Tibial nerve: Produces plantarflexion and sole-of-foot deficits.

D. Saphenous nerve: Is purely cutaneous and cannot cause foot drop.

Exam pearl: Dorsiflexion plus eversion loss near fibular neck = common fibular neuropathy.

Examiner trap: L5 radiculopathy can mimic it; test tibialis posterior inversion.

Viva extension — Which branch supplies tibialis anterior?
Answer: Deep fibular nerve.

Question 16 of 40 • Deep fibular nerve sensory

Q16. After an anterior ankle injury, dorsiflexion is weak but eversion remains intact. Where would isolated deep fibular sensory loss be expected?

A. First dorsal web space between the great and second toes B. Sole of foot C. Lateral foot border D. Medial leg E. Most of foot dorsum except first web space

View detailed explanation, examiner trap and viva

Correct answer: A. First dorsal web space between the great and second toes.

Why correct: Deep fibular nerve supplies anterior-compartment muscles and a small cutaneous patch in the first web space.

Why the other options are incorrect:

B. Sole of foot: Supplied mainly by tibial-derived medial/lateral plantar nerves.

C. Lateral foot border: Mainly sural nerve distribution.

D. Medial leg: Saphenous nerve territory.

E. Most of foot dorsum except first web space: Typically superficial fibular nerve distribution.

Exam pearl: First dorsal web space = deep fibular sensory landmark.

Examiner trap: Intact eversion can distinguish deep fibular from common fibular lesions.

Viva extension — Which branch supplies foot eversion?
Answer: Superficial fibular nerve via fibularis longus/brevis.

Question 17 of 40 • Superficial fibular nerve

Q17. An ankle sprain leads to diminished sensation over most of the dorsal foot, but first web-space sensation is normal. Which nerve is affected?

A. Deep fibular nerve B. Superficial fibular nerve C. Sural nerve D. Saphenous nerve E. Medial plantar nerve

View detailed explanation, examiner trap and viva

Correct answer: B. Superficial fibular nerve.

Why correct: Superficial fibular supplies anterolateral leg and most dorsal foot skin, sparing the first dorsal web space supplied by deep fibular nerve.

Why the other options are incorrect:

A. Deep fibular nerve: Predominantly sensory to first web space.

C. Sural nerve: Supplies the lateral border of the foot.

D. Saphenous nerve: Supplies the medial foot/leg.

E. Medial plantar nerve: Supplies plantar medial sole, not broad dorsum.

Exam pearl: Most dorsal foot = superficial fibular; first web = deep fibular.

Examiner trap: Dorsal foot has overlapping sensory borders, so clinical testing samples discrete zones.

Viva extension — Which movements can also be weak?
Answer: Eversion via fibularis longus and brevis.

Question 18 of 40 • Tibialis posterior

Q18. A patient cannot invert the foot and stand on tiptoe after a tibial-nerve injury. Which muscle is normally important for inversion and medial arch support?

A. Fibularis longus B. Tibialis anterior C. Tibialis posterior D. Extensor hallucis longus E. Fibularis brevis

View detailed explanation, examiner trap and viva

Correct answer: C. Tibialis posterior.

Why correct: Tibialis posterior is a deep posterior compartment muscle supplied by tibial nerve; it inverts/plantarflexes and supports the medial longitudinal arch.

Why the other options are incorrect:

A. Fibularis longus: Mainly everts and plantarflexes, with a transverse arch role.

B. Tibialis anterior: Inverts but dorsiflexes, and is supplied by deep fibular nerve.

D. Extensor hallucis longus: Extends great toe and assists dorsiflexion.

E. Fibularis brevis: Mainly everts foot, rather than inverting it.

Exam pearl: Tibialis posterior = tibial nerve, inversion and arch support.

Examiner trap: Inversion is not purely a tibial-nerve function: tibialis anterior also contributes.

Viva extension — Which tendon can fail in adult acquired flatfoot?
Answer: Posterior tibial tendon.

Question 19 of 40 • Posterior leg compartments

Q19. A penetrating injury damages the tibial nerve within the deep posterior leg compartment. Which movement would be most affected?

A. Ankle dorsiflexion and toe extension B. Foot eversion alone C. Knee extension D. Ankle plantarflexion and toe flexion E. Hip abduction

View detailed explanation, examiner trap and viva

Correct answer: D. Ankle plantarflexion and toe flexion.

Why correct: The tibial nerve supplies posterior-compartment plantarflexors and toe flexors, as well as plantar intrinsic foot muscles.

Why the other options are incorrect:

A. Ankle dorsiflexion and toe extension: Deep fibular nerve/anterior-compartment functions.

B. Foot eversion alone: Superficial fibular nerve/lateral compartment.

C. Knee extension: Femoral nerve/quadriceps.

E. Hip abduction: Superior gluteal nerve/gluteus medius-minimus.

Exam pearl: Tibial nerve = posterior calf and sole.

Examiner trap: Tibial neuropathy can impair both sole sensation and plantarflexion depending on injury level.

Viva extension — What reflex uses the tibial nerve and S1 predominantly?
Answer: Achilles tendon reflex.

Question 20 of 40 • Sural nerve

Q20. A patient has isolated numbness along the posterolateral calf and lateral foot after a superficial nerve injury. Which nerve is most likely injured?

A. Saphenous nerve B. Deep fibular nerve C. Medial plantar nerve D. Femoral motor branch to quadriceps E. Sural nerve

View detailed explanation, examiner trap and viva

Correct answer: E. Sural nerve.

Why correct: The sural nerve is cutaneous and runs near the small saphenous vein to the lateral malleolus and lateral foot.

Why the other options are incorrect:

A. Saphenous nerve: Supplies medial leg/foot.

B. Deep fibular nerve: Sensation to first dorsal web space.

C. Medial plantar nerve: Supplies the medial sole.

D. Femoral motor branch to quadriceps: Would produce motor weakness rather than isolated lateral-foot cutaneous symptoms.

Exam pearl: Sural nerve = lateral foot border sensation, usually no major motor loss.

Examiner trap: Lateral foot sensation is not the same as broad dorsal foot sensation.

Viva extension — Which superficial vein accompanies it near the calf?
Answer: Small saphenous vein.

Question 21 of 40 • Tarsal tunnel borders

Q21. An endurance runner has burning plantar-foot paraesthesia, worsened by prolonged standing, and a positive Tinel sign behind the medial malleolus. Which nerve is compressed?

A. Tibial nerve B. Deep fibular nerve C. Superficial fibular nerve D. Saphenous nerve E. Sural nerve

View detailed explanation, examiner trap and viva

Correct answer: A. Tibial nerve.

Why correct: The tibial nerve travels through the fibro-osseous tarsal tunnel beneath the flexor retinaculum and divides into plantar nerves.

Why the other options are incorrect:

B. Deep fibular nerve: Runs anteriorly across the ankle toward first web space.

C. Superficial fibular nerve: Crosses the lateral/anterior ankle to dorsal foot.

D. Saphenous nerve: Cutaneous along medial leg/foot, outside the tunnel.

E. Sural nerve: Posterolateral ankle and lateral foot territory.

Exam pearl: Tarsal tunnel is posterior to medial malleolus; plantar symptoms suggest tibial involvement.

Examiner trap: Do not confuse this with anterior tarsal tunnel/deep fibular compression.

Viva extension — Name the classic tendon–vessel–nerve order behind medial malleolus.
Answer: Tibialis posterior, flexor digitorum longus, posterior tibial vessels, tibial nerve, flexor hallucis longus.

Question 22 of 40 • Tarsal tunnel contents

Q22. In the tarsal tunnel, which tendon is most posterior among the classic medial-malleolar sequence?

A. Tibialis posterior B. Flexor hallucis longus C. Flexor digitorum longus D. Tibialis anterior E. Fibularis brevis

View detailed explanation, examiner trap and viva

Correct answer: B. Flexor hallucis longus.

Why correct: From anterior to posterior behind the medial malleolus lie tibialis posterior, flexor digitorum longus, posterior tibial vessels, tibial nerve and flexor hallucis longus.

Why the other options are incorrect:

A. Tibialis posterior: Most anterior tendon of the group.

C. Flexor digitorum longus: Lies anterior to the neurovascular bundle.

D. Tibialis anterior: Passes in the anterior ankle extensor compartment.

E. Fibularis brevis: Runs posterior to the lateral malleolus.

Exam pearl: Tom, Dick, And Very Nervous Harry maps tendon-vessel-nerve sequence.

Examiner trap: The FHL is a tendon, not the posterior tibial vessel.

Viva extension — What creates the tunnel roof?
Answer: Flexor retinaculum.

Question 23 of 40 • Dorsalis pedis landmark

Q23. When checking the dorsalis pedis pulse, which tendon usually lies immediately medial to the artery on the dorsal foot?

A. Tibialis posterior tendon B. Flexor hallucis longus tendon C. Extensor hallucis longus tendon D. Fibularis longus tendon E. Achilles tendon

View detailed explanation, examiner trap and viva

Correct answer: C. Extensor hallucis longus tendon.

Why correct: The dorsalis pedis artery is typically palpated just lateral to extensor hallucis longus tendon on the dorsum of the foot.

Why the other options are incorrect:

A. Tibialis posterior tendon: Passes posterior to the medial malleolus, not dorsal foot.

B. Flexor hallucis longus tendon: Runs posterior/plantar toward great toe.

D. Fibularis longus tendon: Travels lateral ankle and plantar foot.

E. Achilles tendon: Is posterior to ankle rather than dorsal.

Exam pearl: Dorsalis pedis pulse is classically lateral to EHL tendon.

Examiner trap: Arterial anatomical variation occurs; absent palpation alone does not diagnose acute ischaemia.

Viva extension — Which leg artery continues as dorsalis pedis?
Answer: Anterior tibial artery.

Question 24 of 40 • Posterior tibial pulse

Q24. The posterior tibial arterial pulse is palpated at which landmark?

A. Anterior to the lateral malleolus B. Just lateral to EHL on dorsum C. Over greater trochanter D. Posterior and inferior to the medial malleolus E. In popliteal crease only

View detailed explanation, examiner trap and viva

Correct answer: D. Posterior and inferior to the medial malleolus.

Why correct: Posterior tibial artery passes deep to the flexor retinaculum behind the medial malleolus, between flexor tendons and tibial nerve.

Why the other options are incorrect:

A. Anterior to the lateral malleolus: Not the posterior tibial artery course.

B. Just lateral to EHL on dorsum: Site of dorsalis pedis artery.

C. Over greater trochanter: A bony hip landmark with no superficial posterior tibial pulse.

E. In popliteal crease only: The popliteal artery is proximal, not the posterior tibial ankle pulse.

Exam pearl: Posterior tibial = behind medial malleolus; dorsalis pedis = dorsal foot.

Examiner trap: Check both distal pulses in trauma, not just dorsalis pedis.

Viva extension — From which artery does posterior tibial arise?
Answer: Terminal branch of popliteal artery.

Question 25 of 40 • Plantar fascia attachment

Q25. A patient with plantar heel pain is tender at the medial calcaneal tubercle. Which structure is classically involved?

A. Achilles insertion B. Deltoid ligament C. Anterior talofibular ligament D. Long plantar ligament only E. Plantar aponeurosis origin

View detailed explanation, examiner trap and viva

Correct answer: E. Plantar aponeurosis origin.

Why correct: The central band of plantar fascia arises from the medial calcaneal tubercle and supports the foot longitudinal arch.

Why the other options are incorrect:

A. Achilles insertion: Inserts posteriorly into calcaneus, not the plantar-medial fascial origin.

B. Deltoid ligament: Medial ankle stabiliser, not plantar heel fascia.

C. Anterior talofibular ligament: Lateral ankle ligament from fibula to talus.

D. Long plantar ligament only: Runs from calcaneus toward cuboid/metatarsals; not the same central fascial origin.

Exam pearl: Plantar fascia originates at medial calcaneal tubercle.

Examiner trap: Distinguish plantar fasciopathy from tarsal tunnel neuropathy by symptom pattern.

Viva extension — What is the windlass mechanism?
Answer: Great toe dorsiflexion tensions plantar fascia and elevates medial arch.

Question 26 of 40 • Lateral ankle ligament

Q26. An inversion–plantarflexion ankle sprain most frequently damages which lateral ligament first?

A. Anterior talofibular ligament B. Deltoid ligament C. Posterior talofibular ligament D. Spring ligament E. Anterior inferior tibiofibular ligament

View detailed explanation, examiner trap and viva

Correct answer: A. Anterior talofibular ligament.

Why correct: ATFL resists anterior talar translation especially in plantarflexion, explaining its frequent injury in inversion sprains.

Why the other options are incorrect:

B. Deltoid ligament: Medial ankle complex mainly injured with eversion/external rotation mechanisms.

C. Posterior talofibular ligament: Strong posterior lateral ligament usually injured in severe mechanisms.

D. Spring ligament: Supports talar head and medial longitudinal arch.

E. Anterior inferior tibiofibular ligament: A syndesmotic ligament injured with rotational high-ankle sprains.

Exam pearl: ATFL = commonest lateral ligament injured in inversion-plantarflexion sprain.

Examiner trap: CFL becomes important in inversion resistance near neutral/dorsiflexion.

Viva extension — Which exam manoeuvre assesses ATFL laxity?
Answer: Anterior drawer of the ankle.

Question 27 of 40 • Femoral artery bifurcation

Q27. After passing deep to the inguinal ligament, the external iliac artery becomes the femoral artery. Which branch supplies much of the deep thigh and gives circumflex branches?

A. Inferior epigastric artery B. Profunda femoris (deep femoral) artery C. Posterior tibial artery D. Dorsalis pedis artery E. Superior gluteal artery

View detailed explanation, examiner trap and viva

Correct answer: B. Profunda femoris (deep femoral) artery.

Why correct: Profunda femoris is the principal deep-thigh branch of the femoral artery and contributes to thigh perforators and circumflex femoral systems.

Why the other options are incorrect:

A. Inferior epigastric artery: Branches from external iliac superior to ligament, supplying abdominal wall.

C. Posterior tibial artery: Arises from popliteal artery in leg.

D. Dorsalis pedis artery: Distal continuation of anterior tibial artery.

E. Superior gluteal artery: Branch of internal iliac via pelvis.

Exam pearl: Profunda femoris = dominant deep-thigh supply.

Examiner trap: Remember femoral artery is continuation of external iliac below ligament.

Viva extension — What is the femoral artery called after adductor hiatus?
Answer: Popliteal artery.

Question 28 of 40 • Lateral circumflex femoral nerve relation

Q28. During anterior hip surgery, a surgeon must consider the branches of the lateral circumflex femoral artery near which muscular interval?

A. Posterior to soleus at ankle B. Within tarsal tunnel C. Between tensor fasciae latae and sartorius/rectus femoris region D. Between gastrocnemius heads alone E. Within first dorsal interosseous foot space

View detailed explanation, examiner trap and viva

Correct answer: C. Between tensor fasciae latae and sartorius/rectus femoris region.

Why correct: Branches of the lateral circumflex femoral artery traverse proximal anterior thigh near the internervous interval used in anterior hip approaches and may require haemostasis.

Why the other options are incorrect:

A. Posterior to soleus at ankle: Soleus belongs to calf, not hip interval.

B. Within tarsal tunnel: Medial ankle tunnel contains posterior tibial vessels.

D. Between gastrocnemius heads alone: Popliteal fossa rather than anterior hip exposure.

E. Within first dorsal interosseous foot space: Distal forefoot, not proximal hip vessels.

Exam pearl: Know the anterior hip interval and ascending lateral circumflex branches.

Examiner trap: Surgical intervals and individual vascular variation matter more than memorising one fixed vessel position.

Viva extension — Which nerve supplies tensor fasciae latae?
Answer: Superior gluteal nerve.

Question 29 of 40 • Great saphenous vein

Q29. A saphenous vein is harvested for grafting. At the ankle, where is the great saphenous vein typically located?

A. Posterior to lateral malleolus B. Deep to tarsal tunnel retinaculum C. Directly under Achilles tendon D. Anterior to the medial malleolus E. Anterior to fibular head only

View detailed explanation, examiner trap and viva

Correct answer: D. Anterior to the medial malleolus.

Why correct: The great saphenous vein courses anterior to the medial malleolus and ascends the medial leg with saphenous nerve close by.

Why the other options are incorrect:

A. Posterior to lateral malleolus: Describes short/small saphenous vein region.

B. Deep to tarsal tunnel retinaculum: Posterior tibial neurovascular bundle passes there, not superficial great saphenous.

C. Directly under Achilles tendon: Not its usual superficial medial path.

E. Anterior to fibular head only: Not the ankle landmark asked about.

Exam pearl: Great saphenous: anterior medial malleolus; small saphenous: posterior lateral malleolus.

Examiner trap: Harvest risks sensory injury to accompanying saphenous nerve.

Viva extension — Where does great saphenous vein drain proximally?
Answer: Femoral vein at the saphenofemoral junction.

Question 30 of 40 • Small saphenous vein

Q30. A superficial vein runs behind the lateral malleolus and along the posterior calf, often draining into the popliteal vein. Identify it.

A. Great saphenous vein B. Femoral vein C. Anterior tibial vein D. Deep plantar venous arch E. Small saphenous vein

View detailed explanation, examiner trap and viva

Correct answer: E. Small saphenous vein.

Why correct: The small saphenous vein arises from lateral dorsal venous arch, passes posterior to lateral malleolus and ascends posterior calf, often entering popliteal vein.

Why the other options are incorrect:

A. Great saphenous vein: Runs anterior to medial malleolus to femoral vein.

B. Femoral vein: Deep thigh vessel, not superficial posterolateral ankle vein.

C. Anterior tibial vein: Deep anterior leg venous system.

D. Deep plantar venous arch: Located in sole, not superficial calf.

Exam pearl: Small saphenous vein tracks with sural nerve on posterior calf.

Examiner trap: Saphenopopliteal drainage is anatomically variable.

Viva extension — Which sensory nerve accompanies it?
Answer: Sural nerve.

Question 31 of 40 • L5 radiculopathy vs fibular neuropathy

Q31. A patient with foot drop has weak ankle inversion as well as dorsiflexion and eversion. Which finding favours an L5 root lesion over isolated common fibular neuropathy?

A. Weak tibialis posterior inversion B. First web-space paraesthesia C. Eversion weakness D. Dorsiflexion weakness E. Fibular-neck tenderness

View detailed explanation, examiner trap and viva

Correct answer: A. Weak tibialis posterior inversion.

Why correct: Tibialis posterior is tibial-nerve innervated but has prominent L5 root input; weakness suggests a lesion proximal to common fibular nerve.

Why the other options are incorrect:

B. First web-space paraesthesia: Can occur in deep fibular/common fibular lesions too.

C. Eversion weakness: Typical of superficial/common fibular nerve injury.

D. Dorsiflexion weakness: Occurs in both L5 root and common fibular neuropathy.

E. Fibular-neck tenderness: Suggests local fibular compression, not L5 root alone.

Exam pearl: Test inversion via tibialis posterior when localising foot drop.

Examiner trap: Tibialis anterior inversion is confounded by its deep fibular innervation; isolate tibialis posterior.

Viva extension — What additional muscle can suggest L5 radiculopathy?
Answer: Gluteus medius (hip abduction), among others.

Question 32 of 40 • Femoral neck retinacular vessels

Q32. An elderly patient with a displaced subcapital femoral neck fracture develops osteonecrosis months later. Which anatomical structure was most likely disrupted?

A. Genicular anastomosis B. Posterior-superior retinacular vessels along femoral neck C. Anterior tibial artery D. Saphenous nerve E. Femoral canal lymphatics

View detailed explanation, examiner trap and viva

Correct answer: B. Posterior-superior retinacular vessels along femoral neck.

Why correct: Retinacular branches, mainly arising from medial circumflex femoral artery, ascend along femoral neck capsule and can tear in displaced intracapsular fractures.

Why the other options are incorrect:

A. Genicular anastomosis: Supplies knee region rather than femoral head.

C. Anterior tibial artery: Supplies anterior leg and dorsalis pedis.

D. Saphenous nerve: Is sensory and does not supply blood.

E. Femoral canal lymphatics: Carry lymph in groin, not head perfusion.

Exam pearl: Retinacular vessel interruption explains femoral-head AVN risk.

Examiner trap: Femoral neck fractures affect vascularity differently from intertrochanteric fractures.

Viva extension — Where does ligamentum teres artery arise most commonly?
Answer: From obturator system (via acetabular branch), contribution varies.

Question 33 of 40 • Popliteus action

Q33. In an extended knee, which muscle assists unlocking the knee to initiate flexion?

A. Rectus femoris B. Gastrocnemius C. Popliteus D. Vastus medialis E. Tibialis anterior

View detailed explanation, examiner trap and viva

Correct answer: C. Popliteus.

Why correct: Popliteus internally rotates the tibia on femur in non-weight-bearing knee, or externally rotates femur on fixed tibia, reversing terminal extension locking.

Why the other options are incorrect:

A. Rectus femoris: Extends the knee and flexes hip, not knee unlocking.

B. Gastrocnemius: Flexes knee and plantarflexes ankle but is not the key locking-release mechanism.

D. Vastus medialis: Extends knee and aids patellar stability.

E. Tibialis anterior: Dorsiflexes/inverts ankle rather than acting on knee.

Exam pearl: Popliteus unlocks the knee.

Examiner trap: Open-chain tibial internal rotation contrasts with closed-chain femoral external rotation.

Viva extension — What nerve supplies popliteus?
Answer: Tibial nerve.

Question 34 of 40 • Trendelenburg alternative

Q34. After injury to a pelvic nerve, a patient leans trunk toward the affected hip during stance and pelvis drops contralaterally. Which muscle group is weak?

A. Hip adductors only B. Quadriceps only C. Hamstrings only D. Hip abductors: gluteus medius and minimus E. Tibialis anterior only

View detailed explanation, examiner trap and viva

Correct answer: D. Hip abductors: gluteus medius and minimus.

Why correct: Ipsilateral abductor weakness causes contralateral pelvic drop and compensatory trunk lean toward stance limb to reduce moment arm.

Why the other options are incorrect:

A. Hip adductors only: Weak adduction does not produce the classic stance-side pelvic stabilisation failure.

B. Quadriceps only: Causes knee buckling rather than primary pelvic tilt pattern.

C. Hamstrings only: Affects knee flexion and hip extension, not principal frontal-plane pelvis control.

E. Tibialis anterior only: Causes foot drop and high-stepping gait.

Exam pearl: Compensated Trendelenburg includes trunk lean toward weak side.

Examiner trap: A pelvic drop alone can reflect pain, weakness or structural issues; clinical context matters.

Viva extension — Which nerve is most relevant?
Answer: Superior gluteal nerve.

Question 35 of 40 • Compartment anatomy

Q35. A patient has pain on passive toe extension after a tibial fracture, with tense deep posterior calf. Which deep posterior compartment structure is at risk?

A. Deep fibular nerve alone B. Dorsalis pedis artery C. Femoral nerve D. Common fibular nerve at fibular neck E. Tibial nerve and posterior tibial vessels

View detailed explanation, examiner trap and viva

Correct answer: E. Tibial nerve and posterior tibial vessels.

Why correct: Deep posterior compartment contains tibialis posterior, toe flexors, tibial nerve and posterior tibial vessels; expanding pressure may compromise these structures.

Why the other options are incorrect:

A. Deep fibular nerve alone: Travels in anterior compartment.

B. Dorsalis pedis artery: In dorsal foot beyond anterior leg.

C. Femoral nerve: Located in anterior thigh, not deep posterior calf.

D. Common fibular nerve at fibular neck: Is superficial near proximal lateral knee rather than central deep posterior calf.

Exam pearl: Compartments matter for ischaemia, passive stretch pain and fasciotomy anatomy.

Examiner trap: Normal pulses do not exclude acute compartment syndrome.

Viva extension — Name the four leg compartments.
Answer: Anterior, lateral, superficial posterior and deep posterior.

Question 36 of 40 • Plantar nerve injury

Q36. Following medial plantar surgical exposure, the patient loses sensation over the medial three and a half toes on the sole. Which nerve is implicated?

A. Medial plantar nerve B. Lateral plantar nerve C. Deep fibular nerve D. Saphenous nerve E. Sural nerve

View detailed explanation, examiner trap and viva

Correct answer: A. Medial plantar nerve.

Why correct: The medial plantar branch of tibial nerve supplies sensation to medial plantar sole and approximately medial 3.5 toes, plus several intrinsic muscles.

Why the other options are incorrect:

B. Lateral plantar nerve: Supplies lateral plantar sole and approximately lateral 1.5 toes.

C. Deep fibular nerve: Sensation to first dorsal web space, not sole.

D. Saphenous nerve: Supplies medial foot edge and leg rather than most medial sole toes.

E. Sural nerve: Supplies lateral dorsal foot and lateral border.

Exam pearl: Medial plantar nerve resembles median nerve distribution in the hand.

Examiner trap: Dorsal toe-tip sensory territories can overlap, but plantar 3.5 toes is classic.

Viva extension — Which nerve supplies most intrinsic plantar foot muscles?
Answer: Lateral plantar nerve (except medial-plantar supplied group).

Question 37 of 40 • Achilles reflex

Q37. A clinician taps the Achilles tendon and finds an absent ankle jerk. Which root contributes most to this reflex?

A. L2 B. S1 C. L3 D. L4 only E. C8

View detailed explanation, examiner trap and viva

Correct answer: B. S1.

Why correct: The Achilles reflex arc travels through tibial nerve and predominantly S1 with some S2 contribution; loss suggests S1 pathway or peripheral nerve pathology.

Why the other options are incorrect:

A. L2: More prominent in proximal thigh/hip and upper lumbar reflex roles.

C. L3: Contributes to patellar reflex via femoral nerve.

D. L4 only: Dominant patellar reflex contribution, not primary Achilles.

E. C8: Cervical root affecting upper limb, not Achilles tendon reflex.

Exam pearl: Knee jerk L3–L4; ankle jerk S1.

Examiner trap: Reflex loss is localising but not disease-specific.

Viva extension — What is the efferent nerve of the Achilles reflex?
Answer: Tibial nerve.

Question 38 of 40 • Fibularis longus tunnel

Q38. A tendon passes posterior to lateral malleolus, crosses beneath the cuboid and inserts on base of first metatarsal/medial cuneiform. Which tendon is it?

A. Fibularis brevis B. Tibialis posterior C. Fibularis longus D. Extensor hallucis longus E. Flexor digitorum longus

View detailed explanation, examiner trap and viva

Correct answer: C. Fibularis longus.

Why correct: Fibularis longus courses behind lateral malleolus then plantar to cuboid via its groove toward medial foot, supporting eversion and transverse arch.

Why the other options are incorrect:

A. Fibularis brevis: Inserts at fifth metatarsal base without crossing under cuboid.

B. Tibialis posterior: Passes behind medial malleolus to navicular/medial midfoot insertions.

D. Extensor hallucis longus: Travels dorsally to distal phalanx of hallux.

E. Flexor digitorum longus: Passes medial ankle to lateral four toes plantar surface.

Exam pearl: Fibularis longus crosses plantar cuboid to first ray.

Examiner trap: Differentiate longus from brevis distal insertion.

Viva extension — What nerve innervates fibularis longus?
Answer: Superficial fibular nerve.

Question 39 of 40 • Femoral pulse landmark

Q39. A clinician palpates the femoral artery at the midpoint between the ASIS and pubic symphysis. What is this surface landmark called?

A. Midpoint of inguinal ligament B. Greater trochanter tip C. Ischial tuberosity D. Mid-inguinal point E. Fibular neck

View detailed explanation, examiner trap and viva

Correct answer: D. Mid-inguinal point.

Why correct: The mid-inguinal point is halfway between anterior superior iliac spine and pubic symphysis and approximates femoral artery location deep to inguinal ligament.

Why the other options are incorrect:

A. Midpoint of inguinal ligament: Halfway between ASIS and pubic tubercle; not identical to mid-inguinal point.

B. Greater trochanter tip: Lateral hip landmark far from femoral artery pulse.

C. Ischial tuberosity: Posteroinferior pelvic landmark.

E. Fibular neck: Lateral knee landmark of common fibular nerve.

Exam pearl: Mid-inguinal point: ASIS to pubic symphysis; ligament midpoint: ASIS to pubic tubercle.

Examiner trap: A common examiner trap is confusing the pubic symphysis with pubic tubercle.

Viva extension — What structure lies immediately medial to femoral artery near ligament?
Answer: Femoral vein.

Question 40 of 40 • Sciatic nerve root

Q40. A patient has posterior hip dislocation with new sciatic nerve palsy. Which root combination forms the sciatic nerve?

A. L1–L3 B. C5–T1 C. S3–S5 only D. L2–L4 E. L4–S3

View detailed explanation, examiner trap and viva

Correct answer: E. L4–S3.

Why correct: The sciatic nerve arises from the sacral plexus with ventral rami L4–S3 and gives tibial and common fibular divisions.

Why the other options are incorrect:

A. L1–L3: More consistent with upper lumbar plexus territories.

B. C5–T1: Brachial plexus roots for upper limb.

C. S3–S5 only: Too caudal; not sciatic root span.

D. L2–L4: Common root pattern of femoral and obturator nerves.

Exam pearl: Sciatic roots = L4 to S3.

Examiner trap: Sciatic palsy after hip dislocation requires documentation before and after reduction.

Viva extension — Which hip dislocation direction commonly risks sciatic injury?
Answer: Posterior dislocation.

Frequently asked questions

How many options are in an MRCS Part A SBA?

Five options, A to E, and one single best answer; these 40 questions are original practice, not actual recalled papers.

What are the best nerve localisation clues in foot drop?

Test dorsiflexion, eversion, tibialis posterior inversion, hip abduction and the first dorsal web-space sensory patch. Examine the whole limb; localisation can be proximal to fibular nerve.

Which injury is classic after fibular neck fracture?

Common fibular neuropathy resulting in dorsiflexion and eversion weakness; check neurovascular function and consider associated compartment or knee injury.

Which structures make femoral NAVEL?

Lateral to medial: femoral Nerve, Artery, Vein, Empty femoral canal and Lymphatics; the nerve lies outside femoral sheath.

How is quiz progress saved?

Checklist ticks and quiz answers are saved using localStorage in this browser, not linked to an account. Progress can be lost when browser storage is cleared.

References and related MRCS articles

References below are for source checking. Uploaded MRCS recall files informed topic priorities; their inherited answers were not accepted without anatomical checking. These are original educational questions.

1. Intercollegiate MRCS Candidate Guidance — Official MRCS Part A scope and syllabus.
2. TeachMeAnatomy: Femoral Triangle — Triangle boundaries, sheath and contents.
3. TeachMeAnatomy: Popliteal Fossa — Neurovascular bundle and applied fossa anatomy.
4. TeachMeAnatomy: Common Fibular Nerve — Fibular neck injury and foot drop localisation.
5. TeachMeAnatomy: Deep Fibular Nerve — Dorsiflexion and first dorsal web space.
6. TeachMeAnatomy: Tarsal Tunnel — Posteromedial ankle retinaculum and tibial nerve.
7. AO Surgery Reference: Posterolateral Hip Approach — Sciatic nerve protection and posterior capsule considerations.
8. NCBI Bookshelf: Femoral Triangle — Independent anatomical reference for vascular sheath.

FreeMedSite MRCS Academy — published lessons

Article 01
Start MRCS Here Article 02
Complete Syllabus Article 03
Books and Resources Article 04
12-Week Study Plan Article 05
SBA Question Strategy Article 06
Common Preparation Mistakes Article 07
Surgical Anatomy Overview Article 08
Upper Limb Anatomy Article 09
Inguinal & Abdominal Wall Article 10
Head & Neck Surgical Anatomy Article 11
Cardiovascular & Respiratory Physiology Article 12
Renal & Acid–Base Physiology Article 13
GI, Endocrine & Neurophysiology

Previous article: Article 13 — GI, Endocrine and Neurophysiology.

Next planned: Article 15 — Thoracic, Pelvic and Visceral Surgical Anatomy. This link will be added after publishing; do not guess the Blogger URL.

Editorial revision 16 October 2026. Educational resource; not a patient-specific emergency-management protocol.