Generalised osteoarthritis: an evolutionary problem?

Polyarticular osteoarthritis (OA) has a distinctive pattern of joint involvement. Some joints, such as the first metatarsophalangeal joint, are commonly affected, whereas others, such as the shoulder, are rarely involved. This distinct pattern of involvement may represent a subset of OA--generalised OA. Analysis of the pattern of change in joint function in the recent evolutionary development of man suggests a hypothesis that explains the pattern of joint involvement in generalised OA. Joints most commonly affected have undergone recent rapid evolutionary change to a new function that has resulted in increased loading. These joints are therefore relatively underdesigned, have little functional reserve, and are likely to fail often and early. Joints that are rarely affected have changed to a function with reduced loading. They are relatively overdesigned and have a large functional reserve, so fail rarely and late.