Knee extension and stiffness in osteoarthritic and normal knees

This study aimed to quantify the response of participants with and without knee osteoarthritis (OA) to a single session of manual physical therapy. The intervention consisted mainly of joint mobilization techniques, supplemented by exercises, aiming to improve knee extension. Participants with knee OA had restricted knee extension range of motion at baseline, in contrast to the participants with normal knees, who had full knee extension. Following the therapy session, there was a significant increase in knee motion in participants with knee OA (P = .004) but not in those with normal knees (P = .201). For stiffness data, there was no main effect for time (P = .903) or load (P = .274), but there was a main effect of group (P = .012), with the participants with healthy knees having greater stiffness than those with knee OA. Reliability, using intraclass correlation coefficient model 3,3, for knee angle measurements between imaging sessions for all loading conditions was 0.99. Reliability (intraclass correlation coefficient model 3,1) for intraimage measurements was 0.97.

The study found end-range knee extension stiffness to be greater in the participants with normal knees than those with knee OA. The combination of lesser stiffness and lack of motion in those with knee OA, which may indicate the potential for improvement, may explain why increased knee extension angle was seen after a single session of manual therapy in the participants with knee OA but not in those with normal knees. Videofluoroscopy of the knee appears reliable and relevant for future studies attempting to quantify the underlying mechanisms of manual therapy.