Initially, signs of bone spavin may include sporadic and vague hind limb lameness.
This is often just assumed to be a “stiffness” which eases off following exercise. In
some instances it may even be assumed to be due to possible back pain. Some horses
may become uncomfortable on one lead in particular, or may demonstrate stiffness
walking downhill. Horses being used for jumping often refuse to jump.
In many cases lameness worsens, becoming more obvious and consistent. Advanced
cases may have a bony swelling on the hock, typically on the inside (medial aspect) of
the joint. Lameness, although usually worse in one leg, is commonly bilateral.
The affected limb usually lands toe-first, wearing down that foot faster than the other.
The affected limb usually has a shorter, lower arc than the other foot, as the horse is
trying to reduce the painful flexion of the joint, so the leg appears to drag.
Performing a flexion test of an affected limb often produces a temporary worsening of
the lameness. Such a response to a flexion test would be supportive, but not
diagnostic, of bone spavin. A flexion test involves holding the hock in forced flexion
for 30-60 seconds before trotting the horse away immediately