2004 Volume 31 Issue 1 Pages 76-85
To obtain the histopathological findings for contracture mechanism and clarify the effect of stretching, we conducted experiments to observe the histopathological changes in joint components after knee joint immobility in rats.
Sixteen adult, nine-week-old male Wistar rats (body weight: 260 g-285 g) were used for this study. The four rats of the control group were raised normally for two weeks. The other 12 rats had their right knee joints immobilized with a cast fixator for two weeks. The four rats of the contracture group were euthanatized immediately after contracture had been achieved. The four rats of the stretch group were subjected to stretching of the immobilized knee for two weeks. The four rats of the non-stretch group were not subjected to stretching. Stretching consisted of five cycles of 50-second stretching and a 10-second rest. The trunk of the rats of the stretch group was immobilized, and the ankle was stretched in the caudal direction. The knee joints excised after sacrifice were fixed in formalin, decalcified and embedded in paraffin. Staining was done with hematoxylin and examination was by a light microscope.
Atrophy of synoviocytes, fibrosis of the layer underlying the synovium, dilatation, proliferation of the synovium at the cartilage-synovium migration area and congestion of the microvasculature were observed in the contracture group. The stretch group returned to almost normal conditions, but the non-stretch group to a lesser extent. The fibroconnective tissue of the contracture group was denser than that of any other group, and the stretch group improved more than the non-stretch group. However, fibrosis of the stretch group was denser than that of the control group. The surface layer of the articular cartilage in the contracture group showed fibrous proliferation in contrast to that of the control group. The contracture group showed thinner connective tissue between the muscle fibers than any other group. The stretch group improved more than the non-stretch group; on the other hand the connective tissue of the stretch group was thinner than that of the control group.
Histopathological changes in the joint components showing contracture were considered to be secondary disorders caused by the cast fixation in this study. However, the stretch group improved more than the non-stretch group, suggesting that stretching has a beneficial effect on joint contracture.
