The hip is often affected by tubercle, especially in children, and is less frequently attacked by rheumatoid arthritis. As the joint is deeply placed, evidence of swelling in the joint is not an early symptom, and it is generally late in the disease before the tubercular debris makes an exit externally. Pain also, as already pointed out, is often referred to the knee, the hip-joint being sometimes entirely overlooked. Hip disease, therefore, in the early stages, is, to a considerable extent, diagnosed by the position of the limb, and its limited power of movement, and it should be remembered that it is not always easy at a very early stage to differentiate between hip disease and psoas abscess. When the hip-joint is affected, the patient places the limb in the position of greatest ease, and keeps it there, as far as possible, without movement with reference to the pelvis. When the hip-joint is fixed, the limb may still be moved in various directions by means of the spine, and thus the superficial observer is easily deceived as to the fixity of the joint. Hip disease is generally said to present certain stages, and they are at least convenient as a means of describing the disease.

1. In the first stage effusion of fluid has occurred in the joint ; all the ligaments are intact, and, in order to accommodate this fluid, the patient fixes the hip-joint in a position of (a) flexion and (b) abduction (also external rotation), which is that of the greatest capacity of the joint. In order to walk he disguises this position by (a) producing a lordosis curve of the spine, thereby tilting the pelvis downwards, and so obliterating the flexion ; (b) producing a scoliosis curve of the spine, thereby tilting the pelvis down on the affected side, and so obliterating the abduction. Thus this patient, while keeping his hip-joint flexed and abducted on the pelvis, walks with a limb which is apparently straight and parallel to its neighbour by means of a lordosis and scoliosis of his spine. Owing, however, to the tilting downwards of the pelvis on the affected side, the limb appears longer than its neighbour, and this, therefore, is referred to as the stage of apparent lengthening.

2. The effusion of fluid remaining present, but the ligaments becoming affected, while the adductor muscles become reflexly irritated through the obturator nerve, the hip-joint next assumes a position of (a) flexion and (b) adduction. Here the flexion is corrected as before, while the adduction is corrected by a scoliosis curve of the spine in a direction opposite to the previous one, so that the pelvis is now tilted up on the affected side. Thus the limb again appears straight, but, owing to the tilting of the pelvis, shorter than its neighbour, and so this period' is referred to as that of apparent shortening.

3. In the late stages of the disease either (a) a pathological dislocation of the head on to the dorsum or (b) destruction of the head occurs. In both cases there is shortening, and this stage is therefore referred to as that of actual shortening, (a) Here the limb becomes fixed in a position of flexion and adduction, which the patient conceals as in (2). (b) Here the limb frequently is straight and perhaps everted, the condition being practically that of pathological fracture of the neck of the femur.

The debris from tubercular hip disease may make its escape in various directions. While it sometimes causes a fulness under the femoral vessels close to Poupart's ligament, it generally escapes from the posterior portion of the joint, and then may work its way forward between the gluteus minimus and the bone and point in front of the great trochanter, or may make its way backwards and point in the gluteal region. When it does escape from the capsule in front, it may enter the sheath of the ilio-psoas, or, if it escapes through the acetabulum, it may work its way up under the obturator and iliac fascia, and so point above Poupart's ligament. In either of these cases it might lead to confusion with real psoas abscess.

Where the disease in the hip-joint has led to extensive destruction of cartilage, excision of the hip-joint is performed. This is best done through a single incision in the line of the limb when flexed and adducted, made just above the great trochanter down on to the head of the bone. The capsule is thus only split at one point, the head of the bone removed by a fan-shaped osteotome, the cut neck is rounded off, all debris removed from the acetabulum, and the limb put up in a position of abduction and extension. The abduction fixes the cut neck against the acetabulum, thus facilitating fibrous union between the two surfaces. The operation as performed for disease is easy and quickly done, and excellent results as regards subsequent movement are obtained when an operation is done at a comparatively early stage of the disease.

Amputation at the hip is best performed by a racket incision, which commences about 2 inches above the great trochanter, runs down over it for about 6 inches, and is then made to encircle the limb skin deep. The muscles surrounding the great trochanter are next divided on either side, the hip-joint exposed and opened, the ligamentum teres divided, the head of the bone forced out, and kept out by introducing a pad of gauze into the acetabulum. The muscles are then divided circularly, and the limb removed (Jordan's amputation). Bleeding is controlled by the shut fist of an assistant placed over the termination of the abdominal aorta, the assistant standing on a stool and leaning the weight of his body on it through his straight arm (Macewen). The muscles divided are the adductors, hamstrings, quadriceps, sartorius, tensor fasciae femoris, ilio-psoas, pectineus, glutei, obturator, gemelli, and pyriformis. If the muscles be stitched together after the amputation, a remarkably mobile stump is obtained. The vessels which require ligature are the femoral and profunda, the circumflexes and branches from them and from the sciatic, and the first perforating of the profunda. The nerves divided are the anterior crural, external cutaneous, and obturator branches in front, and the sciatic nerves behind.