Cellular mechanisms of bone damage and repair in the arthritic joint.

Trabeculae and subchondral bone have been studied by scanning electron microscopy (EM) and fluorescence microscopy from joints removed surgically in patients with rheumatoid arthritis (RA), osteoarthritis (OA), and "normals" who had leg amputations with no primary arthritis. In the arthritic specimens, inflammation, bone damage and repair varied in different areas of the same joint. Osteoclasts and mononuclear cells were associated with areas of resorption--together and separately. Scanning EM showed trabeculae in RA to be thinner, narrower, fewer, and with spindle forms compared with thicker trabeculae in OA. Attempts at repair were more successful in OA despite the higher bone turnover which occurred locally at the rheumatoid joint.