A histological study of human femoral condylar articular cartilage.

Paraffin sections cut both parallel to and perpendicular to the surface were used to study the histological structure of the articular cartilage of the lateral femoral condyle of infants, children and adults. Two main cell types were present--fusiform chondrocytes lying in swirling patterns were the predominant cell type of the cartilage up to and including two years, while a more rounded cell, randomly arranged, was commoner in the older specimens. Evidence suggests that these cells represent two distinct populations of chondrocyte, the round cells being derived from the earlier fusiform cells. Cartilage canals were a feature of the deeper regions of the presumptive articular cartilage in young specimens in which the epiphysis was still cartilaginous. The basophilic tidemark which marks the junction between the calcified and uncalcified cartilage in perpendicular sections was not seen in parallel sections. The calcified cartilage layer contained numerous processes of vascular bone which extended up from the subchondral bone and were a characteristic feature of the cartilage-bone interface. This layer of the articular cartilage cannot therefore be considered to be truly avascular.