OSTEOARTHRITIC CARTILAGE CONTAINS INCREASED CALCIUM, MAGNESIUM AND PHOSPHORUS

Abstract

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.