This may occur to either one or the other separately, or to both at the same time, when the muscles to which they belong are over-fatigued, and fail to act in time and with sufficient force to prevent excessive traction on the tendons.

The hand familiar with the horse's leg will have but little difficulty in distinguishing between injury of either or both of these structures, and those strains of ligaments adjacent which have already been described. They are found to be swollen, hot, and softer than in health, and the enlargement, in bulging backwards as well as laterally, gives the tendons a convex or "bowed" appearance (fig. 367). Lameness is always present in recent cases, and during the inflammatory stages which supervene upon the accident; but there are many chronic sprains of these structures of a slowly progressive character which do not render a horse unworkable or even palpably lame to the ordinary observer. They have been described as coming "unstitched", by which term we are to suppose that in overworked horses a softening and weakening process is induced in the tendons by long-abiding strain and irritation, and a few fibres at a time rupture here and there, and not in any particular line or order. In these cases the action is at first stilty, or, as it is sometimes expressed, "proppy", and sooner or later there is a disposition to "knuckle over" at the fetlocks in the animal's attempt to take the weight off the injured tendons and throw it forward more immediately on to the bony columns.

Fig. 367. - Sprain of the Perforans and Perforatum Tendons.

Treatment

The means advised for sprains of the suspensory and check ligaments are suitable for injuries to the back tendons, as the per-forans and perforatus are called.