Studies in osteoarthritis of the hip. II. Osteoarthritis of the hip and leg-length disparity.

An x-ray method is described for the determination of leg-length inequality in the standing subject, Its precision is compared to that of other methods in current use. The geometrical considerations which are inherent in any radiographic method of leg-length determination are summarized. Sixty-seven patients with OA hip were studied; 62 were considered to be idiopathic and 36 of these idiopathic cases were superolateral in type. Measurements in these 36 patients showed significant leg-length disparity, most of the diseased hips being found on the side of the longer leg. If allowance is made for shortening due to disease, the frequency and bias of the disparity are highly significant. The strong association between OA hip of this type and a long leg suggests a causal relationship.