An abscess may appear _in the thigh_ in front or behind the joint. The _anterior abscess_ emerges on one or other side of the psoas muscle; from the resistance offered by the fascia lata, the pus may gravitate down the thigh before perforating the fascia. It has occasionally happened that when such an abscess has been opened and become infected with pyogenic organisms, the femoral vessels have been eroded, and serious or even fatal hæmorrhage has resulted. The _posterior abscess_ appears in the buttock and may make its way to the surface through the gluteus maximus; more often it points at the lower border of this muscle in the region of the great trochanter, or it may gravitate down the thigh. Abscesses which form _within the pelvis_ originate either in connection with the acetabulum or in relation to the psoas muscle where it passes in front of the joint. Those that are directly connected with disease of the acetabulum may remain localised to the lateral wall of the pelvis, or may spread backwards towards the hollow of the sacrum. They may open into the bladder or rectum, or may ascend into the iliac fossa and point above Poupart's ligament (Fig. 115), or descend towards the ischio-rectal fossa. The abscess which develops in relation to the psoas muscle may be shaped like an hour-glass, one sac occupying the iliac fossa, the other filling up Scarpa's triangle, the two sacs communicating with each other through a narrow neck beneath Poupart's ligament. So long as the skin is intact, the abscess is unattended with symptoms, and may escape notice. If it bursts externally, pyogenic infection is almost inevitable, and the patient gradually passes into the condition of hectic fever or chronic toxæmia; he loses ground from day to day, may become the subject of waxy disease in the viscera, or may die of exhaustion, tuberculous meningitis, or general tuberculosis. #Dislocation# is a rare complication of hip disease, and is most likely to occur during the stage of adduction with inversion. It has been known to take place during sleep, apparently from spasmodic contraction of muscles. In the dorsal dislocation, which is the most common form, adduction and inversion are exaggerated, the trochanter projects above and behind Nélaton's line, and the head of the bone may be felt on the dorsum ilii. It is a striking fact that after dislocation has occurred there is less complaint of pain or of startings than before, and passive movements may be carried out which were previously impossible.