Experimental osteoarthritis in the rabbit: comparison of different periods of repeated immobilization.

The objective of this study was to compare the degree of osteoarthritis caused by different periods of repeated immobilization and mobilization. Existing knowledge of the pathogenic factors causing osteoarthritis is deficient, but it is well known that long-term immobilization produces degenerative joint changes. In this experimental study it is shown that short repetitive periods of immobilization also induce osteoarthritis. The results can be summarized as follows: immobilization, periodic or continuous, over more than 30 days will lead to progressive osteoarthritis. The range of motion after periodic immobilization depends more on the total immobilization time than on the duration of either the immobilization or mobilization periods. Even an immobilization period of 4 days had a cumulative effect in producing osteoarthritis. An interval of 4 weeks between immobilization periods did not prevent immobilization from causing osteoarthritis. It can be assumed that all situations which lead to the immobilization of a joint can cause osteoarthritis changes. Radiology, photography, and histology all showed some degree of degenerative changes also in the contralateral non-immobilized knee.