Effect of differences in tendon properties on functionality of the passive stay apparatus in horses.

Objective: To determine the effect of differences in structural and mechanical tendon properties on functionality of the passive stay apparatus in horses.

Sample: 5 forelimbs each from nondwarf Friesians, dwarf Friesians, and ponies.

Procedures: Harvested forelimbs were loaded to test the passive stay apparatus.

The equine hind limb is actively stabilized during standing.

Horses spend much of their life standing, and they are believed to be able to keep their limbs straight without muscular effort. We tested the hypothesis that the stifle (knee) and hock (tarsal) joints could be stabilized merely with the help of a passive lock mechanism whereby the patella is secured behind a hook, formed by the medial femoral trochlea. In anaesthetized animals and isolated limbs the stifle and hock flex readily under compression.