Question 165

Question:

A man pushes a piano across the floor. At the wrist, the force is transmitted from the carpal bones to the radius. At the elbow, the force is transmitted from the ulna to the humerus. Which of the following structures transmits the force from the radius to the ulna?

Correct Answer: E.  Interosseous membrane

The interosseous membrane (E) is a fibrous sheet between the radius and ulna, forming the radio-ulnar syndesmosis. It divides the forearm into anterior and posterior compartments, and transmits force from the radius to the ulna.

The annular ligament (A) comes off the lateral side of the ulna and encircles the proximal radius. It prevents translation of the proximal radius during pronation, and has no effect on axial forces like the force described here.

The bicipital aponeurosis (B), a.k.a. lacertus fibrosus, extends medially from the biceps tendon to reinforce the cubital fossa. It does not transmit force from the radius to the ulna.

The flexor retinaculum (C), a.k.a. transverse carpal ligament, forms the roof of the carpal tunnel. It does not transmit force from the radius to the ulna.

The intermuscular septum (D) is one of two (lateral or medial) structures arising from the humerus, separating the anterior and posterior compartments of the upper arm. It does not transmit force from the radius to the ulna.