Effects of millimeter-wave for preventing joint stiffness in the immobilized knee rat model.

Aim: To explore the effects and mechanism of millimeter-wave treatment on the development of joint stiffness in the immobilized knee rat model.

Methods: Twenty-four Sprague-Dawley (SD) rats were randomly divided into the control group (O, n = 8), the surgical control group (OC, n = 8), and the millimeter-wave treatment group (MO, n = 8). After immobilized knee modeling, the knee mobility and quadriceps diameter was measured at the 6th week. Hematoxylin and eosin and Masson staining were performed to detect the pathology and fibrous lesions of the knee joint. Furthermore, the expression of TGF-β1 and Collagen I was quantified by immunohistochemical assay in the knee capsule, and Western blotting was performed to quantify the protein expression of NF-κB and MuRF1 in skeletal muscle.

Results: Compared with the O group, knee mobility, and quadriceps diameter was decreased (P < 0.01), and articular capsule fibrosis and quadriceps atrophy occurred in all rats with fixed knee joints. Compared with the OC group, millimeter-wave treatment significantly increased articular mobility and the quadriceps diameter; and improved the fibrotic lesions of the joint capsule and quadriceps atrophy. Moreover, levels of TGF-β1, Collagen I, and MuRF1 were upregulated (P < 0.01) by knee immobilization, and collagen fiber content in the articular capsule was also increased (P < 0.01). However, millimeter-wave treatment reversed it. The most noteworthy result was that NF-κB expression was not significantly different in all groups.

Conclusion: Millimeter-wave treatment reversed joint contracture and quadriceps atrophy caused by joint fixation, inhibited TGF-β1 and Collagen I protein expression of the joint capsule and reduced MuRF1 expression of the quadriceps muscle, thereby inhibiting the development of joint stiffness.