It is probable that both genetic and environmental factors play some part in the aetiology of most cases of degenerative hip disease. Geneticists have identified some single gene disorders of the hip, but have had difficulty in identifying the genetics of many of the common causes of degenerative hip disease. The heterogeneity of the phenotypes studied is part of the problem. A detailed classification of phenotypes is proposed. This study is based on careful documentation of 2003 consecutive total hip replacements performed by a single surgeon between 1972 and 2000. The concept that developmental problems may initiate degenerative hip disease is supported. The influences of gender, age and body mass index are outlined. Biomechanical explanations for some of the radiological appearances encountered are suggested. The body weight lever, which is larger than the abductor lever, causes the abductor power to be more important than body weight. The possibility that a deficiency in joint lubrication is a cause of degenerative hip disease is discussed. Identifying the phenotypes may help geneticists to identify genes responsible for degenerative hip disease, and eventually lead to a definitive classification.

1. The results of thirty-five acutely slipped upper femoral epiphyses, treated from 1950 to 1969, are presented. Avascular necrosis of the femoral head occurred in five cases.

2. Skin traction with medial rotation, followed in three to four days by internal fixation, without further manipulation, is recommended so that this iatrogenic complication may be avoided.

1. Seventy-six patients with fracture of the upper end of the femur were examined phlebographically for evidence of thrombosis. The patients were randomly divided into two groups : one was given phenindione post-operatively ; the other acted as a control.

2. Analysis of the select series showed that the incidence of venous thrombosis in the anticoagulation group (19 per cent) was significantly less than that in the control group (48 per cent).

3. However, analysis of the complete series failed to show that the incidence of venous thrombosis in the anticoagulation group was significantly less than in the control group.

4. The number of bleeding complications in the anticoagulation group (47 per cent) exceeded those in the control group (16 per cent). The only life-endangering haemorrhage occurred in a patient who had not received an anticoagulant for five months.

5. We were unable to show that the fracture significantly influenced the site or the incidence of venous thrombosis.

6. No correlation was found between the clinical and phlebographic diagnosis of venous thrombosis.

7. It is concluded that the early use of a prophylactic anticoagulant is an effective means of reducing the incidence of venous thrombosis in patients with a fracture about the hip.