Experimental osteoarthritis in the rabbit. A study of 133xenon washout rates from the synovial cavity.

Synovial perfusion in 6 rabbit knees, with experimentally induced osteoarthritis (joint instability), was studied by recording the initial 133Xe washout rates from the joint space. The unstable osteoarthritic knee was compared with the contralateral sham operated control knee at intervals of 6 to 96 weeks postoperatively. Within the first half year the ratio between the 133Xe washout rates in the osteoarthritic and control joints was significantly increased. These findings were supported by the increased blood flow to the joint region, visualized by scintigraphy of osteoarthritic rabbits given 99mTc-microspheres intracardially. However, methodological sources of error do not allow any conclusions regarding the much less increased 133Xe washout rates found in advanced osteoarthritis. The initially increased synovial blood flow coincided with the existence of joint effusion and the early development of osteophytes, all conditions supposed to be a consequence of posttraumatic synovitis. Attention is drawn to these pathogenic phenomena in studies dealing with the initial changes in experimental models of osteoarthritis and to a possible etiological significance.