CCEP Anatomy & Biomechanics of Extremities 4 — Questions and Answers
Question 1: During closed-chain pronation of the foot, what obligatory motion occurs at the tibia?
- External rotation
- Internal rotation (Correct answer)
- Anterior translation
- Posterior translation
Correct answer: Internal rotation
Closed-chain subtalar pronation causes obligatory internal rotation of the tibia, which in turn stresses the knee and hip in a predictable kinetic chain.
Question 2: The 'unhappy triad' (O'Donoghue's triad) of the knee classically involves injury to which three structures?
- ACL, PCL, and lateral meniscus
- ACL, MCL, and medial meniscus (Correct answer)
- ACL, LCL, and lateral meniscus
- PCL, MCL, and medial meniscus
Correct answer: ACL, MCL, and medial meniscus
The classic unhappy triad involves the ACL, MCL, and medial meniscus, typically from a valgus contact force applied to a planted foot.
Question 3: Which muscle is the primary supinator of the forearm when the elbow is extended?
- Biceps brachii
- Supinator (Correct answer)
- Brachioradialis
- Pronator teres
Correct answer: Supinator
With the elbow extended, the biceps brachii has a poor mechanical advantage, making the supinator muscle the primary supinator of the forearm.
Question 4: The hip joint's close-packed position (maximum congruency and ligamentous tension) occurs in which position?
- Flexion, abduction, and external rotation (Correct answer)
- Extension, abduction, and internal rotation
- Extension, adduction, and internal rotation
- Flexion, adduction, and internal rotation
Correct answer: Flexion, abduction, and external rotation
The close-packed position of the hip is full extension combined with slight abduction and internal rotation, where the ligaments are most taut.
Question 5: The pes anserinus is the conjoined insertion of which three muscles at the proximal medial tibia?
- Sartorius, gracilis, and semitendinosus (Correct answer)
- Sartorius, gracilis, and semimembranosus
- Gracilis, semitendinosus, and biceps femoris
- Rectus femoris, sartorius, and gracilis
Correct answer: Sartorius, gracilis, and semitendinosus
The pes anserinus ('goose's foot') is formed by the conjoined tendons of the sartorius, gracilis, and semitendinosus inserting on the proximal medial tibial shaft.
Question 6: Which intercarpal joint is most commonly implicated in carpal instability and has the highest risk of avascular necrosis when fractured?
- Trapezoid
- Hamate
- Scaphoid (Correct answer)
- Lunate
Correct answer: Scaphoid
The scaphoid has a tenuous retrograde blood supply; its waist and proximal pole fractures carry significant risk of avascular necrosis and carpal instability.
Question 7: In gait analysis, 'Trendelenburg gait' results from weakness of which muscle group?
- Hip flexors on the stance-side
- Hip abductors on the stance-side (Correct answer)
- Knee extensors on the swing-side
- Ankle plantarflexors on the stance-side
Correct answer: Hip abductors on the stance-side
Weakness of the stance-side hip abductors (primarily gluteus medius) prevents pelvis stabilization, causing contralateral pelvic drop (Trendelenburg sign) or trunk lean.
CCEP Anatomy & Biomechanics of Extremities 4
During closed-chain pronation of the foot, what obligatory motion occurs at the tibia?