Which structures are most frequently involved in stay apparatus-related lameness?

Which structures are most frequently involved in stay apparatus-related lameness?

• A. Proximal suspensory region, distal sesamoidean ligaments behind the fetlock, and the suspensory apparatus around the metacarpus.
• B. Carpal bones and the distal phalanx.
• C. The dorsal laminae only.
• D. Deep digital flexor tendon alone.

Answer: (A)

The stay apparatus relies on a set of passive ligaments and connections that lock the limb so the horse can stand with little muscular effort. The structures most often involved in stay apparatus-related lameness are the proximal suspensory region (the proximal suspensory ligament and its supporting structures at the back of the cannon), the distal sesamoidean ligaments behind the fetlock, and the suspensory apparatus around the metacarpus (the interosseous ligament and its attachments to the sesamoids). When these components are damaged or degenerate, the limb’s stay mechanism is compromised, leading to pain and abnormal weight-bearing that are typical of stay-related lameness. The other structures listed—carpal bones and the distal phalanx, the dorsal laminae, or the deep digital flexor tendon alone—are not the primary components of the stay mechanism, so they’re less likely to be the main source of this specific type of lameness.