The risk of post-traumatic osteoarthritis (PTOA) and associated joint degeneration after ACL injury is high, with roughly 50% of individuals experiencing symptoms 10 to 20 years after injury. Efforts to mitigate PTOA risk after ACL injury have been stalled by the lack of sensitive, specific, and affordable early imaging markers. The current clinical gold standard Kellgren-Lawrence (KL) grading scale that utilizes frontal view radiographs is limited due to its reliance on 2D projection of 3D structures. The introduction of low-dose weight bearing computed tomography (WBCT) has made the imaging of joints in functionally loaded positions readily available, allowing for 3D analysis of joint space narrowing in load-bearing regions. WBCT shows promise for early PTOA detection enhancing earlier intervention.

The objective of this study is to utilize a previously developed fully automated method to measure tibiofemoral 3D pose and joint space width (JSW) from WBCT to assess PTOA risk following ACL reconstruction (ACLR). Bilateral WBCT scans were acquired in a semi-flexed (~20°) and fully extended scan pose for subjects at 3-months and 1-year after ACLR. 3D JSW was evaluated between scan poses and timepoints for the ACLR and intact contralateral knees. A semi-automated method to regionally assess JSW values was utilized to evaluate knee kinematics and the relationship of regional JSW values over the 9-month scan period. Further, regions of narrow JSW were used to nominally define the joint center of contact (CoC) in each tibiofemoral compartment. The CoC was then evaluated between scan poses and time-points to evaluate the influence of ACLR on the screw-home mechanism (SHM) in the knee at terminal extension. The establishing of new WBCT-based 3D imaging markers that reliably and affordably assess PTOA risk and can detect degenerative joint changes earlier can facilitate more effective interventions.