Analysis of Single Knee Model Based on Finite Element Method: Effects of Knee Bending Angle and Load Distribution on Stress and Strain of Tibial Plateau

Background Knee osteoarthritis (OA) pain is often activity-dependent, indicating that joint biomechanics are highly influenced by knee posture and loading conditions. Understanding how tibial plateau stress and strain change dynamically with flexion angle and load distribution is crucial for elucidating the pathogenesis of OA and optimizing non-surgical and surgical interventions. Objective This study aimed to investigate the stress and strain distribution in the tibial plateau under different knee flexion angles and loading conditions using finite element analysis, to provide mechanical insights into the symptomatic progression of OA. Methods A parametric finite element model of a healthy adult knee was developed. Simulations were conducted across various flexion angles (0°, 30°, 45°, 60°) under two load distribution ratios: a normal ratio (60% medial/40% lateral) and an OA-simulated ratio (85% medial/15% lateral). The effects of increasing load magnitude at each angle were also assessed. Results The study revealed a nonlinear relationship between flexion angle and mechanical response. Under normal loading, peak stress increased with flexion, while maximum strain was minimized at 45°. However, under OA-like loading (85/15), the angle for minimum strain shifted to 60°, and a surprising reduction in peak stress was observed at high flexion angles (45° and 60°) despite increased load. This indicates a fundamental shift in load-bearing mechanisms in the diseased knee. Conclusion These findings provide a biomechanical explanation for why OA patients may experience less pain in deep flexion activities (e.g., squatting) despite higher loads, as the stress on the tibial plateau may actually decrease. This study highlights the importance of evaluating knee mechanics throughout the range of motion, rather than solely in a static posture. The results offer valuable insights for planning targeted rehabilitation exercises and for improving the biomechanical rationale behind procedures like high tibial osteotomy.