Knee Extension and Stiffness in Osteoarthritic and Normal Knees: A Videofluoroscopic Analysis of the Effect of a Single Session of Manual Therapy

STUDY DESIGN: Descriptive biomechanical study using an experimental repeated-measures design. OBJECTIVE: To quantify the response of participants with and without knee osteoarthritis (OA) to a single session of manual physical therapy. The intervention consisted primarily of joint mobilization techniques, supplemented by exercises, aiming to improve knee extension. (D BACKGROUND: While manual therapy benefits patients with knee OA, there is limited research quantifying the effects of a manual therapy treatment session on either motion or stiffness of osteoarthritic and normal knees. METHODS: The study included 5 participants with knee OA and 5 age-, gender-, and body mass index-matched healthy volunteers. Knee extension motion and stiffness were measured with videofluoroscopy before and after a 30-minute manual therapy treatment session. Analysis of variance and intraclass correlation coefficients were used to analyze the data. RESULTS: 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. After 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. CONCLUSION: End-range knee extension stiffness was 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 observed following 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.