The influence of early osteoarthritic collagen network de-structuring in articular cartilage on the tissue stiffness and swelling properties

Abstract

Results: ACLRs and controls had similar participant characteristics (height, age, gender and tested limb-side). Controls had significant positive relationships between maximum walking medial contact forces and both medial cartilage volume ( Fig 1A) (R2¼0.33, b¼0.9, 95% CI 0.32e1.5, p¼0.003) and thickness (R2¼0.17, b¼0.0001, 95% CI 0.000004e0.0003, p¼0.04). ACLRs had no significant relationships in the medial compartment, and the group differences between the relationship slopes were significant (p¼0.02). Neither group had significant relationships in the lateral compartment. Adjusting for the size of the joint did change relationships slightly ( Fig 1B), but controls still had significant positive relationships between contact pressure and cartilage thickness in the medial compartment (R2¼0.22, b¼0.38, 95% CI 0.07e0.70, p¼0.02), while ACLRs had no significant relationships in any compartment. Both ACLRs and controls had significant positive relationships between maximum walking medial tibiofemoral contact forces and medial tibial subchondral bone area ( Fig 1C)(ACLRs R2¼0.11, b¼0.27, 95% CI 0.09e0.45, p¼0.003, controls R2¼0.42, b¼0.63, 95% CI 0.31e0.96, p<0.001), and the slopes of these relationships were significantly different between the two groups (p¼0.025). Conclusions: Compared with healthy controls, ACLRs at 2e3 years post-reconstruction had significantly different relationships between their walking tibiofemoral contact forces and articular tissue morphology. Healthy controls showed significant positive relationships between contact loading and articular cartilage volume, confirming previous in vitro studies, but ACLRs had no such significant relationships. These group differences in the relationships between loading and morphology persisted when adjusting for participant joint size. It is concerning that the normal adaptive response of cartilage may not be occurring in ACLRs as little as 2e3 years post-operation. While the subchondral bone had significant positive relationships with contact loading in both groups, the relationship was statistically weaker in ACLRs. We are currently conducting follow-up studies to explore the relationship between contact forces at 2e3 years post-operation and the change in articular tissue morphology at 4e5 years post-operation.