Treadmill Exercise Suppresses Histological Progression of Disuse Atrophy in Articular Cartilage in Rat Knee Joints during Hindlimb Suspension

Objective The purpose of this study was to determine the preventive effects of treadmill exercise or physiological loading on disuse atrophy in the rat knee joint cartilage and bone during hindlimb suspension. Design Twenty male rats were divided into 4 experimental groups, including the control, hindlimb suspension, physiological loading, and treadmill walking groups. Histological changes in the articular cartilage and bone of the tibia were histomorphometrically and immunohistochemically evaluated 4 weeks after the intervention. Results Compared with the control group, the hindlimb suspension group showed thinning of cartilage thickness, decreased matrix staining, and decreased proportion of noncalcified layers. Cartilage thinning, decreased matrix staining, and decreased noncalcified layers were suppressed in the treadmill walking group. The physiological loading group exhibited no significant suppression of cartilage thinning or decreased noncalcified layers, but the decreased matrix staining was significantly suppressed. No significant prevention of bone mass loss or changes in subchondral bone thickness were detected after physiological loading or treadmill walking. Conclusion Disuse atrophy of the articular cartilage caused by unloading conditions could be prevented by treadmill walking in rat knee joints.