For descriptive purposes lameness may be classified as true and false. True lameness is such as is occasioned by structural or functional defects of some part of the apparatus of locomotion, such as would be caused by spavin, ring-bone, or tendinitis. False lameness is an impediment in the gait not caused by structural or functional disturbances, but is brought on by conditions such as may result from the too rapid driving of an unbridle-wise colt over an irregular road surface, or by urging a horse to trot at a pace exceeding the normal gait of the animal’s capacity, causing it to “crow-hop” or to lose balance in the stride. The latter manifestation might, to the inexperienced eye, simulate true lameness of the hind legs, but in reality, is merely the result of the animal having been forced to assume an abnormal pace and a lack of balance in locomotion is the consequence.
The degree of lameness, though variable in different instances, is in most cases proportionate to the causative factor, and this fact serves as a helpful indicator in the matter of establishing a diagnosis and giving the prognosis, especially in cases of somewhat unusual character. An animal may be slightly lame and the exhibition of lameness be such as to render the cause bafflingly obscure. Cases of this nature are sometimes quite difficult to classify and in occasional instances a positive diagnosis is impossible. Subjects of this kind may not be sufficiently inconvenienced to warrant their being taken out of service, yet a lame horse, no matter how slightly affected, should not be continued in service unless it can be positively established that the degree of discomfort occasioned by the claudication is small and the work to be done by the animal, of the sort that will not aggravate the condition.
Subjects that are very lame—so lame that little weight is borne by the affected member—are, of course, unfit for service and as a rule are not difficult of diagnosis. For instance, a fracture of the second phalanx would cause much more lameness than an injury to the lateral ligament of the coronary joint wherein there had occurred only a slight sprain, and though crepitation is not recognized, the diagnostician is not justified in excluding the possibility of fracture, if the lameness seems disproportionate to the apparent first cause.
The course taken by cases of lameness is as variable as the degree of its manifestation, and no one can definitely predict the duration of any given cause of claudication.
Because of the fact that horses are not often good self-nurses at best, and that it is difficult to enforce proper care for the parts affected, one can not wisely state that resolution will promptly follow in an acute involvement, nor can he predict that the case will or will not become chronic. Experience has proved that complete or partial recovery may result, or again, that no change may occur in any given case, and that in some instances even where rational treatment is early administered, a decided aggravation of the condition may follow unaccountably.