kicks. Horses three or four years of age if given work that favors hock
strain, such as excavating cellars, may develop a spavin.

[Illustration: FIG. 47.--Normal cannon bone and cannon bone showing bony
enlargement and lower hock bones united to superior extremity; this occurs
in bone spavin.]

_The symptoms_ or lameness are more characteristic than in most diseases of
the limb. At the very beginning of the inflammation, and sometimes for
several months afterward, the lameness is intermittent and disappears with
exercise. After a time it is permanent. It is characterized by a stiffness
of the hock. The extension of the hock is incomplete, the step is short and
quick, the animal "goes on its toe" and the wall or shoe at the toe shows
considerable wear. Because of the stiffness in the hock the animal raises
the quarter when the limb is carried forward. Turning toward the well side
may increase the lameness. The _spavin test_ may be of value in diagnosing
lameness. This consists in picking up the foot and holding the hock in a
flexed position for a few minutes. The foot is then dropped to the ground
and the animal moved off at a brisk trot. If the lameness is more marked,
it indicates that the seat is in the region of the hock. This test is of
greatest value in young animals. The bony enlargement can usually be seen
best if the examiner stands in front and to one side of the animal. The
hock should be observed from directly behind as well. The hocks of both
limbs should be compared, and the general conformations of the other joints
as well. This may prevent the examiner from mistaking rough hocks for
spavin enlargements or "a pair" of spavins for rough hocks. A bony
enlargement does not always accompany the lameness, and a spavin may be
present without the horse going noticeably lame.

[Illustration: FIG. 48.--Bog spavins.]