Shear strain and fluid velocity-driven mechanobiological knee joint models can predict local cartilage adaptation after acl injury and reconstruction: numerical predictions compared with longitudinal variations in t1ρ and t2 maps

Traumatic knee injuries often involve cartilage lesions and may lead to post-traumatic osteoarthritis (PTOA). One of the signs of PTOA is the loss of fixed charge density (FCD) of proteoglycans in cartilage. Mechanisms to understand local adaptive processes remain unclear. A numerical model was developed to predict local degeneration of FCD in injured cartilage using maximum shear strain and fluid flow-controlled algorithms. The predictions were compared against T1ρ and T2 maps of magnetic resonance imaging at 1- and 3-years after anterior cruciate ligament reconstruction. The results showed that the FCD content decreased near the lesion for both mechanisms. Likewise, T1ρ and T2 relaxation times increased in similar regions. The novel mechanobiological model provides a novel platform for predicting local FCD loss and PTOA in injured knee joint cartilage.