Turning round, we now direct attention to the posterior aspect of the limb, and the first part requiring notice is the knee. Here we are sometimes confronted with a soft fluctuating swelling on either side, resulting from a distension of the sheath of the tendons with fluid, and commonly termed " thoroughpin" of the knee from its resemblance to that enlargement which appears from time to time above and behind the hock-joint.

The back tendons and ligaments will next come under notice, and as the hand passes over them it should particularly note their condition about the lower part of the upper third of the canon-bone, where the check ligament joins on to the deep flexor tendon (Vol. II, p. 294). This is the point where sprain most frequently takes place, and where the enlargement which results will be felt when it can be detected nowhere else; but in severe sprain the tendon for a greater or less distance along its course towards the fetlock and the knee becomes enlarged and gives to the leg behind a bowed appearance, hence the term " bowed tendon ". A defect of this kind affecting structures of such importance in any part of their course is a serious one, and at once contravenes the animal's soundness. In front of the tendons, and immediately behind the canon-bone, the suspensory ligament (Vol. II, p. 272) will be felt. As we have elsewhere pointed out, this structure divides a little way above the fetlock-joint into an inner and an outer branch, which become inserted into the sesamoid bones behind the fetlock.

Sprain and thickening of this ligament are more especially seen in hunters, chasers, and race-horses. The injury almost invariably occurs either at the point where it divides above the fetlock-joint, or where its branches join the sesamoid bones; but the spread of the inflammatory action from these centres provokes enlargement for varying distances along its coarse, according to the severity of the sprain.

Each individual branch of the ligament should be examined separately and compared with its fellow, and with those of the opposite limb too, lest a slight uniform thickening of the two should be overlooked. Sprain of this ligament is at all times serious, and must be regarded as an unsoundness.