Resist hyper extension of pastern and fetlock joints

Resist hyper extension of pastern and fetlock joints

• A. Seasmoidean ligaments
• B. Navicular ligaments
• C. Medial ligaments
• D. Tendons of digital extensors

Answer: (A)

The proximal sesamoidean ligaments are the key players in resisting hyperextension of the fetlock and pastern. These ligaments wrap around the fetlock joint, connecting the proximal sesamoid bones to the proximal phalanx and cannon bone. When the limb bears weight, they tighten and act as a passive check rein, preventing excessive opening (hyperextension) of the fetlock and pastern. This helps the horse maintain a stable stance with minimal muscular effort as part of the stay apparatus. Other structures don’t provide this specific restraint. Navicular ligaments are tied to the navicular apparatus and coffin joint, not the fetlock/pastern. Medial ligaments are collateral stabilizers that resist sideways movement, not the controlled extension required to prevent hyperextension. Tendons of the digital extensors actively extend joints and thus oppose flexion, rather than serving as the passive restraint to hyperextension.

The proximal sesamoidean ligaments are the key players in resisting hyperextension of the fetlock and pastern. These ligaments wrap around the fetlock joint, connecting the proximal sesamoid bones to the proximal phalanx and cannon bone. When the limb bears weight, they tighten and act as a passive check rein, preventing excessive opening (hyperextension) of the fetlock and pastern. This helps the horse maintain a stable stance with minimal muscular effort as part of the stay apparatus.

Other structures don’t provide this specific restraint. Navicular ligaments are tied to the navicular apparatus and coffin joint, not the fetlock/pastern. Medial ligaments are collateral stabilizers that resist sideways movement, not the controlled extension required to prevent hyperextension. Tendons of the digital extensors actively extend joints and thus oppose flexion, rather than serving as the passive restraint to hyperextension.