Osteoarthritic femoral articular cartilage of knee joint in man.

Osteoarthritis is the most common of the various articular disorders affecting man. The present study was conducted to observe the microstructure of osteoarthritic human femoral articular cartilage by light microscopy. Fifteen osteoarthritic cartilage specimens obtained from patients with primary osteoarthritis (52-80 years) undergoing total knee replacement were processed for paraffin sections. 5 m thick sections were observed under light microscope. The articular surface appeared to be very irregular and fibrillated in all the specimens. The cartilage did not show the normal zonation. Various changes seen were different in all specimens and they were not related to age. Most common feature of the osteoarthritic articular cartilage was the presence of large clusters of cells in 60.0% specimens. Detached parts of the degenerating cartilage were present in the joint cavity in the form of loose bodies. The collagen fibres appeared to be coarser and irregular even near the non-fibrillated areas. Numerous tangential, oblique and vertical splits were also observed. Osteoblastic and osteoclastic activity was seen in the subchondral bone and the osteolytic cyst appeared to invade the cartilage from the subchondral bone. Blood vessels from the subchondral bone were also seen invading the cartilage in 20.0% specimens. The various changes seen in the osteoarthritic cartilage could be an effort of cartilage repair but such attempts are severely counteracted by the osteoarthritic wear process.