Tests on hypotheses about osteoarthritis and hip joints.

Hypotheses suggesting that hip joints which develop osteoarthritis are congruent, have a single area of peak pressure, and have peak pressure which exceeds normal values were tested. Of 100 hip joints examined on necropsy; two showed an early stage of osteoarthritis and the geometry and pressure distribution under load were assessed in these joints. One joint was congruent, in agreement with the hypotheses, but the other was incongruent. In both joints there were several areas of high pressure, the number and location of which depended on the orientation of the joint. The measured values of pressure in the congruent joint exceeded values found previously in normal hip joints. In the incongruent hip joint the peak pressures were within normal limits.