Anatomy Marathon 1 — Lower Limb — Revision Guide: MCQs MCQs

Question 1

Which two structures are attached at the anterior inferior iliac spine (AIIS) of the pelvis?

Accepted Answer

Iliofemoral ligament and straight head of rectus femoris — The iliofemoral ligament and the straight head of rectus femoris both attach at the anterior inferior iliac spine. The sartorius originates instead from the anterior superior iliac spine.

Question 2

A patient sustains a fracture of the neck of the femur and is informed of an increased risk of avascular necrosis. Which vessel group is primarily responsible for supplying the femoral head?

Accepted Answer

Retinacular vessels arising from the extracapsular ring — The femoral head is supplied by retinacular vessels arising from an extracapsular arterial ring formed by the medial and lateral circumflex femoral arteries. Damage to these vessels during a femoral neck fracture leads to avascular necrosis.

Question 3

Which of the following describes the actions of the rectus femoris muscle across the joints it spans?

Accepted Answer

Flexes the hip joint and extends the knee joint — Rectus femoris is a two-joint muscle that acts to flex the hip and extend the knee. Most two-joint muscles in the lower limb have opposite actions at each of the two joints they cross.

Question 4

Which muscle acts to pull the patella medially, thereby helping to resist natural lateral patellar dislocation?

Accepted Answer

Oblique fibers of vastus medialis muscle — The oblique fibres of the vastus medialis pull the patella medially to counteract the lateral pull of the quadriceps mechanism. Other stabilizing factors include the medial patellofemoral ligament and the deep trochlear groove.

Question 5

Which artery gives rise to the perforating branches supplying the posterior thigh muscles as well as the medial and lateral circumflex femoral arteries?

Accepted Answer

Profunda femoris artery — The profunda femoris artery gives off perforating branches for the posterior thigh and circumflex branches for the femoral head. It plays a major role in supplying the deep compartments of the thigh.

Question 6

During a regional nerve block for a perineal procedure, the ischial spine is used as a critical bony landmark. Which nerve is being targeted?

Accepted Answer

Pudendal nerve — The ischial spine serves as the landmark for a pudendal nerve block, which anaesthetises structures of the perineum. The pudendal nerve has root values of S2, S3, and S4.

Question 7

A patient presents with a positive Trendelenburg test, dropping the pelvis on the unsupported side when standing on one leg. Which nerve injury or dysfunction is most commonly associated with this finding?

Accepted Answer

Superior gluteal nerve — A positive Trendelenburg sign results from weakness or paralysis of the hip abductors (gluteus medius and minimus), which are innervated by the superior gluteal nerve. Injury to this nerve leads to contralateral pelvic drop during unilateral stance.

Question 8

Where does the piriformis muscle attach distally after originating from the anterior aspect of the middle three sacral pieces?

Accepted Answer

Tip of the greater trochanter — The piriformis muscle originates from the anterior sacrum and inserts on the tip of the greater trochanter of the femur. It acts primarily to laterally rotate the extended thigh at the hip.

Question 9

Following a supracondylar femoral fracture, the distal bone fragment frequently displaces posteriorly. What is the primary mechanical cause of this displacement?

Accepted Answer

Pull of the gastrocnemius muscle originating from the femoral ridges — The gastrocnemius originates from the supracondylar ridges of the femur and its contraction pulls the distal fragment backward following a supracondylar fracture. This posterior displacement can threaten the popliteal vessels.

Question 10

Which of the following structures contributes to the static stability of the ankle joint?

Accepted Answer

Deltoid ligament of the ankle — The deltoid ligament provides vital static stability on the medial side of the ankle joint, alongside the mortise structure and other collateral ligaments. Tendons crossing the joint provide dynamic rather than static stability.

Question 11

Why does an injury in the middle segment of the plantar aponeurosis or the plantar watershed area tend to heal very slowly?

Accepted Answer

The middle segment possesses a relatively poor intrinsic vascular supply — The plantar watershed area receives blood from muscles proximally and the plantar aponeurosis distally, leaving the middle segment with a poor blood supply. This hypovascularity results in slow healing after injury in this zone.

Question 12

Which of the following anatomical features correctly describes the siding of a human talus bone using the table-top test?

Accepted Answer

With the rounded head pointing forward, the trochlear surface faces upward — The talus can be sided using the table-top test where, with the rounded head pointing forward, the convex/concave trochlear surface faces upward. The talus is also unique in the foot as no muscles insert directly onto its body.

Question 13

Which specific bone of the foot is characterized by having no muscle insertions directly on its body and relies heavily on a retrograde blood supply?

Accepted Answer

Talus — The talus has no muscle tendon insertions directly on it, making it prone to avascular necrosis after neck fractures due to its retrograde blood supply. The calcaneus, by contrast, serves as the insertion point for the Achilles tendon.

Question 14

At which joints do the movements of inversion and inversion-associated eversion of the foot primarily occur?

Accepted Answer

Subtalar and talocalcaneonavicular joints — Inversion and eversion primarily occur at the subtalar and talocalcaneonavicular joints. The talocrural joint functions primarily as a hinge joint for dorsiflexion and plantarflexion.

Question 15

What is the primary innervation of the trapezius muscle?

Accepted Answer

Spinal accessory nerve (CN XI) — The trapezius muscle is innervated by the spinal accessory nerve (CN XI). The thoracodorsal nerve innervates the latissimus dorsi.

Question 16

What are the classic spinal nerve root values for the phrenic nerve?

Accepted Answer

C3, C4, C5 — The phrenic nerve arises from spinal nerve roots C3, C4, and C5, with C4 being the major contributor. This shared root value accounts for referred pain from the diaphragm to the shoulder.

Question 17

Why does gallbladder or diaphragmatic irritation frequently refer pain to the right shoulder skin?

Accepted Answer

Shared spinal cord segments between the phrenic nerve and supraclavicular nerves — Referred pain to the right shoulder occurs because the phrenic nerve shares spinal cord segments with the supraclavicular nerves supplying the shoulder skin. The supracondylar nerves do not supply the shoulder area.

Question 18

A patient presents with a 'winged scapula' following trauma. Which nerve and corresponding muscle are most likely affected?

Accepted Answer

Long thoracic nerve and serratus anterior muscle — Injury to the long thoracic nerve causes paralysis of the serratus anterior muscle, leading to the clinical sign of a winged scapula. The axillary nerve supplies the deltoid and teres minor.

Question 19

Which of the following nerves continues as the lateral cutaneous nerve of the forearm after providing motor innervation to the anterior compartment of the arm?

Accepted Answer

Musculocutaneous nerve — The musculocutaneous nerve terminates as the lateral cutaneous nerve of the forearm, providing sensory supply to the lateral forearm. The median nerve passes into the forearm without giving cutaneous branches in the arm.

Question 20

What is the common origin for the forearm extensor muscles associated with lateral epicondylitis, commonly known as tennis elbow?

Accepted Answer

Lateral epicondyle of the humerus — Tennis elbow or lateral epicondylitis results from excessive or repetitive use of forearm extensor muscles at their common origin on the lateral epicondyle. The medial epicondyle is the origin for flexor muscles.

Question 21

A patient presents with a wrist drop, characterized by unopposed flexion of the hand at the wrist joint. Which nerve is most likely injured?

Accepted Answer

Radial nerve — Radial nerve injury paralyzes the extensor muscles of the wrist and digits, resulting in the characteristic wrist drop. The median nerve injury typically results in an 'hand of benediction' or ape hand.

Question 22

Why does the scapular arterial anastomosis visibly pulsate in cases of coarctation of the aorta?

Accepted Answer

Marked enlargement of subclavian artery branches due to blood being diverted past the coarctation — In coarctation of the aorta distal to the subclavian artery, blood is diverted through the subclavian branches, markedly enlarging and making the collateral vessels of the scapular anastomosis visibly pulsate. This is a classic collateral pathway in coarctation.

Question 23

Which of the following is a non-neurovascular content found within the cubital fossa?

Accepted Answer

Biceps brachii tendon — The tendon of the biceps brachii is a major non-neurovascular content found centrally within the cubital fossa. The median nerve and brachial artery are primary neurovascular structures located in the fossa.

Question 24

What does Tinel's sign clinically indicate when tested over the course of a peripheral nerve?

Accepted Answer

A tingling sensation produced when an irritated or regenerating nerve is tapped — Tinel's sign involves eliciting a tingling sensation by tapping over an irritated or regenerating nerve, which helps test functional recovery. It does not indicate complete nerve transection.

Question 25

Which two arterial branches unite to form the deep palmar arch?

Accepted Answer

Radialis indicis artery and princeps pollicis artery — The radialis indicis and princeps pollicis arteries form the deep palmar arch. The superficial palmar arch is primarily formed by the ulnar artery.

Question 26

Which three structures are classically involved in the 'unhappy triad' injury of the knee described by O'Donoghue?

Accepted Answer

Anterior cruciate ligament, medial collateral ligament, and medial meniscus — The unhappy triad comprises tears of the anterior cruciate ligament, medial collateral ligament, and medial meniscus. Lateral structures are not part of this classic combined knee injury.

Question 27

How are the proximal and distal radio-ulnar joints structurally classified?

Accepted Answer

Pivot synovial joints — The proximal and distal radio-ulnar joints are pivot (uniaxial) synovial joints that act together to allow pronation and supination. Hinge joints only permit flexion and extension.

Question 28

What anatomical feature primarily contributes to the high mobility of the first carpometacarpal joint?

Accepted Answer

Saddle-shaped articular surfaces — The high mobility of the first carpometacarpal joint is due to its saddle-shaped joint surfaces, which permit movement in multiple axes. Plane joints have very limited gliding mobility.

Question 29

Which nerve gives off a cutaneous branch in the popliteal fossa that joins another contribution to supply the lateral side of the foot?

Accepted Answer

Tibial nerve — In the popliteal fossa, the tibial nerve gives off a cutaneous branch that becomes the sural nerve after being joined by a contribution from the common fibular nerve. The sural nerve then supplies the lateral side of the foot.

Question 30

Following a fracture of the proximal leg or popliteal region, posterior displacement of the distal bone fragment is primarily caused by the pull of which muscle?

Accepted Answer

Gastrocnemius — Posterior displacement of the distal fragment in certain fractures is caused by the pull of the gastrocnemius, which originates from the supracondylar ridge. Soleus originates lower down on the tibia and fibula.

Anatomy Marathon 1 — Lower Limb — Revision Guide: MCQs MCQs

Questions, Answers & Explanations