Simulation of surface strain in tibiofemoral cartilage during walking for the prediction of collagen fibre orientation

Abstract

The collagen fibres in the superficial layer of tibiofemoral articular cartilage exhibit distinct patterns in orientation revealed by split lines. In this study, we introduce a simulation framework to predict cartilage surface loading during walking to investigate if split line orientations correspond with principal strain directions in the cartilage surface. The two-step framework uses a multibody musculoskeletal model to predict tibiofemoral kinematics which are then imposed on a deformable model to predict surface strains. The deformable model uses absolute nodal coordinate formulation (ANCF) shell elements to represent the articular surface and a system of spring-dampers and internal pressure to represent the underlying cartilage. Simulations were performed to predict surface strains due to internal pressure, loading induced by walking, and the combination of both loading due to pressure and walking. Peak femoral and tibial cartilage deflections were slightly greater than 1 mm during simulated walking. First principal strain magnitudes within the cartilage surface ranged up to 3%. Time-averaged first principal strains agreed best with split line maps from the literature when surface loading due to internal cartilage pressure was included. This result suggests there may be a connection between pressure-induced surface strain patterns and the collagen fibre orientation patterns that emerge.