THE EVOLUTIONARY ORIGINS OF OSTEOARTHRITIS - A COMPARATIVE SKELETAL STUDY OF HAND DISEASE IN 2 PRIMATES

Objective. To test the evolutionary hypothesis for joint failure by co mparing the prevalence of osteoarthritis (OA) in 2 primate hands with different thumb usage. Methods. We studied the hand skeletons of 32 hu mans and 32 macaques for OA. We defined OA as the presence of joint eb urnation. Results. The prevalence of OA in the distal interphalangeal joints was 26.7 and 50% for humans and monkeys, respectively. For the thumb base it was 37.5% in humans compared with 3.3% in macaques. The relative risk of thumb base OA in humans compared with macaques was 7. 9. Conclusion. The lower prevalence of thumb base OA in macaques may b e due to the rudimentary design of the thumb. This finding supports th e evolutionary hypothesis for joint failure and it may be applicable t o many other joint sites.