Studies in osteoarthritis of the hip. IV. Biomechanics and clinical considerations.

Present knowledge of hip biomechanics supports the contention that the stresses imposed on the hip on the side of the longer leg are greater than normal; those on the short side are comparably reduced. Indirect measurements by various authors have demonstrated greater stress on the hip if the pelvis is adducted, a persistent and chronic condition of the hip joint on the side of a long leg. Furthermore the pressure on the acetabulum will be displaced laterally in these circumstances. The consistent pattern of degeneration in unilateral superolateral O A hip is what would be expected if the consequences of leg-length disparity were as described. Leg-length inequality may be a major contributing factor in the development of unilateral degenerative disease of the hip of this type.A clinical method of estimating leg-length disparity is described. Clinical findings in patients support the hypothesis that hip stress is increased on the side of a longer leg.