The “spavin test” is of value as a diagnostic measure when it is employed with other means of examination, though reaction to this test is seen in some cases in old “crampy” horses that have experienced hard service.  The test consists in flexing the affected leg (elevating the foot from the ground twelve to twenty-four inches) and holding the member in this position for a minute, whereupon the animal is made to step away immediately at a trot.  During the first few steps taken directly thereafter, the subject shows pronounced lameness and this constitutes a reaction to the spavin test.

Where no exostosis is present it becomes necessary to exclude other causes for lameness but the characteristic spavin lameness is to be relied upon to a greater extent in such cases than are other means of examination.  Such cases are known as occult spavin and may be present for months before any external changes in structure are observable.  In some instances no extoses form even during the course of years.  The spavin test is of aid in establishing a diagnosis here but the marked “warming out” peculiar to spavin is not so pronounced in such cases.

Prognosis.—­An animal having hereditary predisposition to spavin is not likely to recover completely whether this predisposition be due to faulty conformation or susceptibility to bone changes.  In predicting the outcome, the temperament of the subject is to be taken into account, as well as the character of service the animal is expected to perform.  And finally, a very important feature to be noted, is the location of the exostosis.  If situated rather high and extending anterior to the hock, there is less likelihood of recovery resulting than where an exostosis is confined to the lower row of tarsal bones.  When situated anterior to the tarsus a large exostosis may by mechanical interference to function, cause lameness when all other causes are absent.  In making examinations one must not be deceived by the inconspicuous and seemingly insignificant exostosis which has a broad base.  In some cases of this kind, dealers style the condition as “rough in the hock” when as a matter of fact, in some instances, incurable spavin lameness develops.

Treatment.—­Many incipient cases of spavin yield to vesication and a protracted period of rest.  Results depend primarily upon the nature of the affection.  However, in every instance if there is involvement of the tibial tarsal (astragalus) bone, complete recovery is highly improbable.  When the disease is confined to the lower tarsal bones, lameness subsides as soon as the degenerative changes are checked and ankylosis occurs.