Which structures form the hind limb reciprocal apparatus and coordinate stay mechanism?

Which structures form the hind limb reciprocal apparatus and coordinate stay mechanism?

• A. Lacertus fibrosus and extensor carpi radialis
• B. Suspensory ligament and distal sesamoidean ligaments
• C. Patellar locking mechanism
• D. Peroneus tertius and the superficial digital flexor tendon

Answer: (D)

The hind limb reciprocal mechanism is built around how two tendinous structures coordinate movement between the stifle and the hock, allowing the limb to move in harmony with minimal muscular effort. The peroneus tertius tendon runs across the stifle and hock and, together with the superficial digital flexor tendon, links these joints so that movement at one joint is matched by the other. When the stifle bends, these tendons guide the hock to flex in concert; when the stifle extends, they help the hock extend as well. This synchronized action is what keeps the limb properly aligned during weight bearing.

Other structures mentioned are part of different aspects of stay mechanisms in either the forelimb or other joints, or are separate locking mechanisms, but they do not form the hind limb reciprocal linkage in the way the peroneus tertius and the superficial digital flexor tendon do.