The clones of osteoarthritic cartilage.

We studied the early cartilage changes in osteoarthritis, examining the most normal appearing articular cartilage from the hips of 17 patients. Normal appearing cartilage from five patients treated for fractures was used as control material. Two different types of clone were found. The first had increased staining for proteoglycan and was thought to have been engaged in the synthesis of matrix. The other type was associated with a severe deficiency of proteoglycan, matrix streaks and evidence of degradation and phagocytosis of matrix components. Immunohistochemistry demonstrated large amounts of chondroitin 4 and 6 sulphate about the synthetic-type clones, and little or no reactivity about the degenerative clones which lay more superficially and were associated with matrix destruction. Clones appeared to be engaged in either matrix synthesis or its destruction. The disease process of osteoarthritis appeared to begin at the surface of the articular cartilage.