Formation process of extension knee joint contracture following external immobilization in rats
Chen-Xu Zhou, Feng Wang, Yun Zhou, Qiao-Zhou Fang, Quan-Bing Zhang
Abstract
BACKGROUND: Current research lacks a model of knee extension contracture in rats. AIM: To elucidate the formation process of knee extension contracture. METHODS: = 6 in each group). The passive extension range of motion, histology, and expression of fibrosis-related proteins were compared between the control group and the immobilization groups. RESULTS: week. Histological analyses confirmed that the anterior joint capsule of the extended fixed knee became increasingly thicker over time. Correspondingly, the level of transforming growth factor beta 1 (TGF-β1) and phosphorylated mothers against decapentaplegic homolog 2 (p-Smad2) in the anterior joint capsule also increased with the immobilization time. Over time, the cross-sectional area of muscle fibers gradually decreased, while the amount of intermuscular collagen and TGF-β1, p-Smad2, and p-Smad3 was increased. Unexpectedly, the amount of intermuscular collagen and TGF-β1, p-Smad2, and p-Smad3 was decreased during the late stage of immobilization (6-8 wk). The myogenic contracture was stabilized after 2 wk of immobilization, whereas the arthrogenic contracture was stabilized after 3 wk of immobilization and completely stable in 4 wk. CONCLUSION: This rat model may be a useful tool to study the etiology of joint contracture and establish therapeutic approaches.