This study aimed to develop a rabbit model of knee contracture in extension and investigate the natural history of motion loss and time-dependent changes in the joint capsule after immobilization. We immobilized the unilateral knee joints of 32 rabbits by maintaining the knee joint in a plaster cast at full extension. Eight rabbits were euthanized at 2, 4, 6, and 8 weeks after casting, respectively, and the lower extremities were disarticulated at the hip joint. Eight control group rabbits that did not undergo immobilization were also examined. We assessed the progression of joint contracture by measuring the joint range of motion, evaluating the histologic alteration of the capsule, and assessing the mRNA levels of transforming growth factor β1 (TGF-β1) in the anterior and posterior joint capsules. After 2 weeks of joint immobilization, the knee joint range of motion was limited, the synovial membrane of the suprapatellar and posterior joint capsules was thickened, the collagen deposition was increased, and the mRNA levels of TGF-β1 were elevated in the anterior and posterior joint capsules. These changes progressed rapidly until 6 weeks of immobilization and may advance slowly after 6 weeks. Joint contracture developed at the early stage of immobilization and progressed over time. The changes in the anterior and posterior joint capsules after joint immobilization may contribute to the limitation in flexion. The elevated mRNA expression of TGF-β1 may be related to joint capsule fibrosis and may be one of the causes of joint contracture.

Stretching combined with ultrashort wave treatment was effective in improving joint range of motion, reducing the biomechanical, histological, and molecular manifestations of joint capsule fibrosis in a rabbit model of extending joint contracture.

BackgroundRecent studies have shown that radial extracorporeal shock wave therapy (rESWT) modulates viability and gene expression of human skeletal muscle cells in vitro. However, the underlying biological effects and mechanisms of rESWT on muscle atrophy and myogenic contracture in animal mode have not yet been investigated. ObjectiveTo investigate the underlying biological effects and mechanisms of rESWT on myogenic contracture and muscle atrophy in a rabbit model of extending knee joint contracture. MethodsForty rabbits were randomly divided into eight groups. In group Control, the left knee joint was not xed.In group I-4w, the left knee joint was only xed for four weeks. In groups SR-1w, SR-2w, and SR-4w, the left knee joint was xed for four weeks before the rabbits underwent one, two, and four weeks of self-recovery, respectively. In groups rESWT-1w, rESWT-2w, and rESWT-4w, the left knee joint was xed for four weeks