Fractures of the _external angle_ of the ileum or point of haunch are usually followed by displacement of the fractured portion. The same is true of fractures of the _neck of the ileum_. The result is a deformity of the quarter. In making an _examination_ of these parts the examiner should see that the horse is standing squarely on its feet, and then compare the conformation of the two quarters. Fractures of either the external angle or the neck of the ileum cause the quarter to appear narrow and low. A close examination may enable the examiner to differentiate between the two fractures. Fractures of the neck of the ileum can be recognized by manipulating the part through the walls of the rectum or vagina. The degree of lameness may vary. In some cases there may be no lameness when the animal walks, but a slight degree of lameness may be noticed when it trots. For several weeks after the injury the horse may be unable to use the limb, but it may eventually make nearly a complete recovery. Atrophy of the muscles of the hip or quarter (Fig. 44) should not be mistaken for fractures of the ileum. This condition involves the heavy gluteal muscles and may occur as a complication of azoturia, or a lameness of the hind limb that is usually due to a spavin. It is very seldom necessary to give fractures of the ileum any special care. If the animal is very lame, it should be given a narrow stall, and placed in a sling until it can support its weight on the limb. The same treatment is indicated in cattle. It is not advisable to breed a mare that has had the ileum fractured. The bony enlargement that results from the union of the broken ends of the bone may interfere with the passage of the foetus through the pelvic cavity and cause difficult parturition. [Illustration: FIG. 44.--Atrophy of the muscles of the quarter.] LUXATION OF THE PATELLA, "Stifle Out."--This is a common accident in horses and mules. Young, immature animals are more prone to displacement of the patella than when mature. The displacement is usually upward or outward. Outward displacement is comparatively rare.