SURFACE CHANGES IN THE ARTICULAR CARTILAGE OF RABBIT KNEE DURING IMMOBILIZATION. A SCANNING ELECTRON MICROSCOPIC STUDY OF EXPERIMENTAL OSTEOARTHRITIS

Osteoarthritis was produced by the immobilization of rabbit knees in extension for 1--8 weeks (with a subsequent mobilization period of 0 or 8 weeks). The development of articular surface changes in the tibia, the femur and the patella was examined with scanning electron microscopy (SEM). During the development of osteoarthritis the normal undulations and fine regular fibre network disappeared, the number of fibres and the variation in the thickness of the fibre bundles increased, and scaly irregularities appeared. Some degenerative changes in the contralateral, non-immobilized hind limb also appeared. The normal features of the articular surface of the patella differed from that of the tibial and femoral condyles. The changes seen with SEM correlated well with histological and biochemical results of earlier studies, but at 1 week of immobilization, the SEM changes were more readilly apparent than the histological changes. The SEM method seems to be useful for the study of articular surfaces; however, the area studied must be defined.