In a study of cartilage from osteoarthritic femoral heads, more than twice as much collagen was extracted by chymotrypsin than from non-osteoarthritic femoral heads13. The molecular nature of this extractable collagen has not been characterized. Therefore, the present study was designed to examine the possibility that collagen type III was prominent in it, to determine the size of the molecular fragments and to explore the potential for insights in OA pathogenesis and the potential for a novel biomarker of the OA process. The availability of well-characterized sets of femoral heads from clinical OA and osteoporotic fracture patients undergoing hip replacement surgery made this collaborative study possible.