Baseline Knee Extension Is Associated With Volumetric Femoral Cartilage Loss in the Central Region of the Mid-lateral and External Medial Femoral Condyles: Data From the Osteoarthritis Initiative

Objective Data evaluating knee flexion contracture (FC)-associated regional changes on femoral articular cartilage are lacking. We compared regional femoral articular cartilage outcomes of people with knee osteoarthritis (OA) with and without FC using quantitative MRI data. Methods Articular cartilage of the medial and lateral femoral condyles were segmented into internal, central, and external subregions on MRI. Goniometry measured knee extension. We tested for regional differences in cartilage thickness and percent denuded bone (i.e., 0mm cartilage thickness) in the presence or absence of FC, and for associations between cartilage outcomes with quantitative knee extension range of motion (ROM) using a linear model for 596 participants. Results For FC versus no FC, cartilage thickness in the central lateral subregion was higher (2.36±0.42mm vs. 2.29±0.43mm; p<0.05), with higher percent denuded bone in the central lateral (0.92±3.5% vs. 0.39±2.2%; p<0.05) and central medial subregions (4.61±12.88% vs. 3.17±11.66%; p<0.05). Lost knee extension was associated with increased percent denuded bone in the internal lateral ( r= 0.095; p<0.05), central lateral ( r =0.90; p<0.05), and central medial subregions ( r =0.117 ; p<0.01) but with increased central lateral cartilage thickness ( r =0.110; p<0.01). After correcting for clinical factors, an association between lost knee extension and increased percent denuded bone remained in the central lateral femur [ β =0.059; (95% CI 0.003–0.114)]. Conclusion Conclusion: Lost knee extension was associated with increased percent denuded bone in the central lateral and external medial femur. Interventions to maintain and/or restore knee ROM may benefit femoral cartilage health. Longitudinal studies evaluating the impact of lost knee ROM on femoral cartilage are warranted.