Where is the interosseous (suspensory) ligament located and what is its function in the hind limb stay apparatus?

Where is the interosseous (suspensory) ligament located and what is its function in the hind limb stay apparatus?

• A. It runs along the medial cannon bone, attaches to the proximal sesamoid bones behind the fetlock, and suspends the fetlock to resist overextension under load.
• B. It connects the navicular bone to the coffin bone.
• C. It encircles the pastern joint and prevents hyperextension.
• D. It attaches to the lateral cannon bone and stabilizes the fetlock.

Answer: (A)

In the hind limb stay apparatus, the key structure that keeps the fetlock from collapsing under load is the suspensory ligament, the interosseous ligament. It runs along the cannon bone (typically on the medial side) and attaches to the proximal sesamoid bones behind the fetlock. When the limb bears weight, this ligament tightens and pulls the proximal sesamoids upward, effectively suspending the fetlock. This tension helps prevent overextension of the fetlock under load, channeling forces through the cannon bone and sesamoids to stabilize the joint during movement.

Other descriptions don’t match this role: connecting the navicular bone to the coffin bone pertains to a different structure, an annular or ring-like arrangement around the pastern describes a different constraint, and attaching to the lateral cannon bone would misstate its common pathway and primary side of emphasis.