Etiology of osteoarthritis of the hip.

More than 90% of patients with so-called primary or idiopathic osteoarthritis of the hips in whom sufficient data were available to make an assessment of the normality of the hip joint at the cessation of growth clearly showed demonstrable abnormalities in the hip joint. The most common are mild acetabular dysplasia and/or pistol grip deformity. This latter deformity is associated with mild slipped capital femoral epiphysis (recognized or unrecognized at the time), Legg-Perthes' disease (recognized or unrecognized at the time), multiple epiphyseal dysplasia, spondyloepiphyseal dysplasia, and/or the presence of an intraacetabular labrum, as well as, in certain instances, acetabular dysplasia. When these abnormalities are taken in conjunction with the detection of other metabolic abnormalities that can lead to osteoarthritis of the hip and which may not be recognized readily, such as hemochromatosis, ochronosis, calcium pyrophosphate disease, and monarticular rheumatoid arthritis, it seems clear that either osteoarthritis of the hip does not exist at all as a primary disease entity or, if it does, is extraordinarily rare.