Histopathological Changes in Joint Components in a Rat Knee Joint Contracture Model Following Mobilization

Abstract

[Purpose] The aim of this study was to investigate the histopathological effects of mobilization on joint components using a rat knee joint contracture model. [Method] Twenty-two male Wistar rats (aged 9 weeks) were randomly divided into an experimental group (n = 18) and a control group (n = 4). The experimental group had the right posterior limb knee joint immobilized for 8 weeks to induce contracture after which this group was subdivided into three subgroups–immobilized, treatment, and non-treatment groups. In the immobilized group (n = 6), knee joint specimens were collected immediately after immobilization. The non-treatment group (n = 6) was bred normally for 8 weeks, while the treatment group (n = 6) underwent mobilization during the same 8 weeks. After breeding, we prepared tissue specimens of the knee joint for observation in the sagittal plane and examined them using a light microscope. [Results] Compared to the non-treatment group, the treatment group showed an increase in the number of fat cells in the synovial subintima and a reduction in the density of collagen fiber bundles in the posterior joint capsule. [Conclusion] Joint mobilization appears to effectively improve joint function.