Spontaneous osteoarthritis in rhesus macaques. II. Characterization of disease and morphometric studies.

From examination of the articular tissue of 35 animals from the Caribbean Primate Research Centre, we identified the epidemiological and histomorphometric features of the spontaneous osteoarthritis (OA) that affects the free-ranging rhesus macaques. The frequency of this disease increases with aging, and in females, with increased parity. Histological and morphological studies demonstrate that as in humans, the disease is characterized by persistence of the chondrocyte density typified by the cartilage of young animals. Owing to its epidemiologic and histologic resemblance to the disease in man, we conclude that degenerative arthritis affecting rhesus macaques provides a useful model for the study of factors contributing to the pathogenesis of OA.

Osteoarthritic cartilage contains increased calcium, magnesium and phosphorus.

Using plasma emission spectroscopy, we measured the calcium (Ca), phosphorus (P), magnesium (Mg), and sulphur (S) concentration in femoral head cartilage from 7 patients with osteoarthritis (OA) and 22 normal patients. We found that in OA cartilage Ca = 271.9 +/- 32.7 mmol/kg dry weight compared to Ca = 113.2 +/- 12.6 mmol/kg dry weight in normal controls. The Ca:P molar ratio in OA cartilage was 1.93 compared to Ca:P = 2.27 in normals, and Ca:P = 1.67 in apatite crystals. We conclude that OA cartilage has a greater binding capacity for Ca, Mg, and P than does normal cartilage. Apatite crystals, if present, comprise maximally 0.4% wet weight of OA cartilage.