EFFECTS OF CONTINUOUS PASSIVE MOTION AND IMMOBILIZATION ON SYNOVITIS AND CARTILAGE DEGRADATION IN ANTIGEN-INDUCED ARTHRITIS

Objective. To determine the effects of continuous passive motion (CPM) and immobilization on synovitis and cartilage degradation in an exper imental model of chronic inflammatory, antigen-induced arthritis. Meth ods. After bilateral arthritis induction of knee joints in 22 NZW rabb its, one knee was immobilized with a flexion splint while the opposite knee received CPM. Results. After 2 weeks (n = 10), the CPM treated k nees had significantly greater joint swelling, synovial effusion, and histologic synovitis scores compared to its opposite immobilized knees , However, the total cartilage degradation score showed no statistical ly significant difference between the two treatments. When the treatme nts were discontinued after 2 weeks and animals were allowed intermitt ent active motion of both knees in cages for 4 weeks (n = 12), no stat istically significant difference in joint swelling, synovial effusion, and histologic synovitis score was observed between the 2 treatments. The articular cartilage degradation, however, was significantly great er in the immobilized knees compared to its opposite CPM treated knees . Five of 12 immobilized knees had articular surface erosion compared to none in the CPM treated knees. Loss of cellularity was also signifi cantly greater in the immobilized knees. Conclusion. Although CPM prod uced greater synovitis at 2 weeks, articular cartilage was better pres erved in the knees treated with CPM than immobilization at 6 weeks.