Which tendons form the reciprocal apparatus in the hind limb stay mechanism?

Which tendons form the reciprocal apparatus in the hind limb stay mechanism?

• A. Peroneus tertius and superficial digital flexor tendon.
• B. Flexor carpi ulnaris and common digital extensor
• C. Deep digital flexor tendon and gastrocnemius
• D. Biceps femoris and semimembranosus

Answer: (A)

The hind limb stay mechanism relies on a reciprocal apparatus that links the stifle and the hock so they move together. This link is formed by the peroneus tertius tendon and the superficial digital flexor tendon. Their connection creates a coordinated system: when the stifle extends, tension through the peroneus tertius pulls on the superficial digital flexor tendon to extend the hock, and when the stifle flexes, the same tendon linkage allows corresponding flexion of the hock. This synchronized action lets the limb bear weight with little muscular effort, effectively “locking” into a stable stance. Other tendon pairings don’t provide this specific cross-link between the stifle and hock, so they don’t form the reciprocal apparatus observed in the stay mechanism.