What components constitute the suspensory apparatus of the horse, and what is its role in the stay mechanism?

What components constitute the suspensory apparatus of the horse, and what is its role in the stay mechanism?

• A. Interosseous (suspensory) ligament, proximal and distal sesamoidean ligaments, and the proximal sesamoid bones
• B. Patellar ligament and extensor tendons
• C. Lacertus fibrosus
• D. Carpal ligaments

Answer: (A)

The stay mechanism relies on a suspensory apparatus that acts like a supportive sling for the fetlock. Its components are the interosseous (suspensory) ligament, the proximal and distal sesamoidean ligaments, and the proximal sesamoid bones. When the limb bears weight, the suspensory ligament stretches and transmits tensile forces through the sesamoidean ligaments to the proximal sesamoid bones, helping to keep the fetlock joint extended. This tension helps support the limb with minimal muscular effort, forming the basis of the stay mechanism that allows the horse to stand quietly. Structures like the patellar ligament or extensor tendons, lacertus fibrosus, and carpal ligaments serve other roles and are not part of the suspensory apparatus involved in the stay mechanism.