The hip is the largest ball-and-socket joint in the body. The ball (the head of the thigh bone) is surrounded to a large extent by the socket in the pelvis, which gives it great stability but means that the ligaments in the hip are not as robust as one would expect in a joint of this size. Hip disorders are an important cause of temporary or permanent disablement. Particularly in older patients. Extra strain on the hip joint may then lead to arthrosis; fractures of the oblique upper part of the thigh bone are also common in the elderly as a result of osteoporosis. Younger people suffer from congenital hip displacement, Perthes’ disease and certain forms of rheumatic inflammation.