Stay Apparatus-Horse Lecture PDF

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Muscles surrounding joints are finely adjusted to maintain balance Large animals have considerable stress in muscle tissue How do large animals accommodate?: - Increase fibrous tissue within muscles that is more resistant to stressful forces - Restrict movement of joints by arrangement of fascia and ligaments so only flexion and extension is possible (with exception of shoulder and hip joint) - Stay apparatus Stay Apparatus - System of tendons, ligaments, and deep fascial tissue which holds legs straigh with minimal muscular activity or fatigue - Flexible and somewhat elastic support - Ability allows instant action when danger threatens - Present in form- and hind limbs - Enables horse to stand for long periods while resting Functions of Stay Apparatus - Supports limb and fetlock - Overcomes tendency of joints to collapse with minimal energy expenditure - Prevents excessive extension of fetlock, pastern, and coffin joints - Helps prevent fatigue of limb muscles by reducing the amount of energy required to keep the limb stable Weight bearing components - Connective tissue, tendons and ligaments - bear weight of animal - By-pass muscles - Eliminate need for energy expenditure of muscle contraction - Muscles can become tired, Connective tissues do not Stay Apparatus of Pelvic Limb - Supports massive amount of weight from main body of horse - Weight centered on femoral head- vertical line intersects the hoof - Stifle joint lies cranially - Hock, fetlock, and pastern lie caudal - Three parts: patellar locking, reciprocal mechanism, and check apparatus

Patellar Locking Mechanism

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Extension of stifle and contraction of lateral muscles Causes patella and medial patellar tendon to move over trochlear tubercle Locks stifle in an extended position Accomplished only one limb at a time Horse must unlock rested limb and shift weight to opposite tiring limb...