The Influence of Obesity and Meniscal Coverage on In Vivo Tibial Cartilage Thickness and Strain

BACKGROUND: Obesity, which potentially increases loading at the knee, is a common and modifiable risk factor for the development of knee osteoarthritis. The menisci play an important role in distributing joint loads to the underlying cartilage. However, the influence of obesity on the role of the menisci in cartilage load distribution in vivo is currently unknown. PURPOSE: To measure tibial cartilage thickness and compressive strain in response to walking in areas covered and uncovered by the menisci in participants with normal body mass index (BMI) and participants with high BMI. STUDY DESIGN: Controlled laboratory study. METHODS: Magnetic resonance (MR) images of the right knees of participants with normal BMI (<25 kg/m(2); n = 8) and participants with high BMI (>30 kg/m(2); n = 7) were obtained before and after treadmill walking. The outer margins of the tibia, the medial and lateral cartilage surfaces, and the meniscal footprints were segmented on each MR image to create 3-dimensional models of the joint. Cartilage thickness was measured before and after walking in areas covered and uncovered by the menisci. Cartilage compressive strain was then determined from changes in thickness resulting from the walking task. RESULTS: Before exercise, medial and lateral uncovered cartilage of the tibial plateau was significantly thicker than covered cartilage in both BMI groups. In the uncovered region of the lateral tibial plateau, participants with high BMI had thinner preexercise cartilage than those with a normal BMI. Cartilage compressive strain was significantly greater in medial and lateral cartilage in participants with high BMI compared with those with normal BMI in both the regions covered and those uncovered by the menisci. CONCLUSION: Participants with high BMI experienced greater cartilage strain in response to walking than participants with normal BMI in both covered and uncovered regions of cartilage, which may indicate that the load-distributing function of the meniscus is not sufficient to moderate the effects of obesity. CLINICAL RELEVANCE: These findings demonstrate the critical effect of obesity on cartilage function and thickness in regions covered and uncovered by the menisci.