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This is the report of a light and transmission electron microscopic study of an olecranon bursitis and of the adjacent distal tricipital tendon in an 83 year-old man. The data are compared with those of a similar study in the same patient performed 2 years ago. Calcium pyrophosphate dihydrate crystals were observed in the bursal fluid, in the inner part of the bursal wall (extracellular localization and intracellular phagocytosis) as well as in the peripheral part of the tendon. In addition, small apatite deposits were observed in the bursa and tendon by electron microscopy. The origin of these bursal deposits is discussed; it is suggested that they may be related to an exchange from the tendon to the remodelled bursal wall.

Cholesterol crystals were identified in 16 synovial fluids from 12 patients who were seen over the 14-year period 1964 through 1977. Ten of the 12 patients had rheumatoid arthritis of a median duration of 12 years. One patient had ankylosing spondylitis and another had iliopectineal bursitis without other joint disease. The fluids were usually turbid, white, or yellow in color and of thick consistency. When the synovial fluid concentration of cholesterol was determined, it was higher than the serum level. The swollen joints and bursae did not respond favorably to simple aspiration or corticosteroid injections but did to surgical synovectomy. No relationship was found between synovial fluid accumulation of cholesterol crystal and previous intra-articular corticosteroid therapy, serum lipoprotein abnormalities, intra-articular hemorrhage, or generalized arteriosclerosis. The results suggest that local factors are most important in the development of synovial fluid cholesterol crystals, but the exact mechanisms are unknown. The presence of cholesterol crystals in synovial fluid should suggest a severe persistent synovitis, knowledge of which may be helpful in diagnosis and planning therapy.