1. Senile subcapital fractures in osteoporotic patients are due to fatigue, not to the impact of a fall, since they are preceded by the local accumulation of isolated trabecular fatigue fractures.

2. One pathological significance of the isolated trabecular fractures described by Todd, Freeman and Pirie (1972) has been demonstrated.

1. The femoral head has been examined in specimens taken from cadavers, patients suffering subcapital fracture of the femoral neck and patients undergoing total replacement arthroplasty for osteoarthrosis and rheumatoid arthritis.

2. Lesions have been seen, some of which appear to be uniting fatigue fractures of individual trabeculae.

3. It is suggested that excessive cyclical loading, sometimes leading to fatigue fractures, may represent a fundamental pathological process of general importance in the evolution of certain skeletal and articular diseases.