AJSM - 2026-07-10 - Journal Article
Quantitative Investigation of Tibiofemoral Cartilage Early Degeneration After ACL Reconstruction: An Integrated Biomechanical and Longitudinal MRI Analysis.
Lin J, Cheng R, Yan Y, Zeng X, Huang W, Tsai TY, Deng C, Wang S, Zhang Y
Topics
Key Takeaway
ACL reconstruction produces persistent posterior displacement of the tibiofemoral contact pressure center (medial 5.29 mm, lateral 4.73 mm) that spatially corresponds to 9–21% focal cartilage thinning on the tibial plateau at 3 years.
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Summary
This study investigated whether altered dynamic contact pressure after ACLR mechanistically drives early cartilage degeneration by combining 3-year longitudinal quantitative MRI in 30 ACLR patients with 6-DOF robotic gait simulation in 8 cadaveric knees. MRI demonstrated significant cartilage thinning across posterior and central tibial subregions bilaterally, with the greatest loss in the internal medial tibia (21%, P=.019). Robotic simulation showed reconstructed knees maintained a posteriorly displaced pressure center throughout the gait cycle and exhibited enlarged contact area in early stance and terminal swing, particularly medially.
Key Limitation
The cadaveric simulation cohort (n=8) is too small and anatomically unmatched to the MRI cohort to confirm that the observed pressure shifts are the direct causal driver of the specific cartilage thinning patterns rather than a correlated finding.
Original Abstract
BACKGROUND
Anterior cruciate ligament reconstruction (ACLR) restores stability but is often followed by early cartilage degeneration. The contribution of altered dynamic contact pressure during gait to this degeneration remains poorly understood.
PURPOSE
To investigate the biomechanical mechanisms underlying early cartilage degeneration after ACLR, with a focus on dynamic contact pressure distribution during gait.
STUDY DESIGN
Controlled laboratory study.
METHODS
In a 3-year longitudinal magnetic resonance imaging (MRI) study of patients with ACLR (n = 30), cartilage thickness of the tibial plateau was quantitatively assessed using deep-learning-based 3-dimensional segmentation techniques. In parallel, cadaveric knees (n = 8) were tested under intact, ACL-deficient, and ACL-reconstructed conditions using a 6 degree-of-freedom robotic simulator replicating gait cycles. Tibiofemoral contact pressure and pressure center trajectories were recorded using pressure-sensitive film.
RESULTS
Quantitative MRI analyses revealed significant cartilage thinning in the posterior tibial subregion 3 years after ACLR. On the medial plateau, the central medial tibia, internal medial tibia, and posterior medial tibia subregions exhibited mean reductions of 10% ( P = .027), 21% ( P = .019), and 13% ( P = .041), respectively. On the lateral plateau, significant decreases were observed in central lateral tibia (9%; P = .031), posterior lateral tibia (14%; P = .029), and external lateral tibia (15%; P = .035). In robotic gait simulations, the reconstructed knees exhibited persistent posterior displacement of the whole-gait-cycle contact center of stress on both tibial plateaus (residual shifts: medial, 5.29 mm; lateral, 4.73 mm; both P < .05). Additionally, the contact area was significantly enlarged in early stance (2%-12% gait cycle) and terminal swing (75%-100%), especially in the medial compartment.
CONCLUSION
ACLR-induced pressure center displacement coincides with focal posterior cartilage degeneration, forming a spatiotemporal mechanical-pathological chain. This work highlights the potential of dynamic loading biomarkers for early osteoarthritis risk stratification and targeted mechanical intervention.
CLINICAL RELEVANCE
Persistent shifts in tibiofemoral pressure centers after ACLR coincide with focal cartilage thinning, suggesting a mechanical pathway to post-ACLR osteoarthritis. Identifying such dynamic loading biomarkers may guide early risk stratification and targeted interventions in sports medicine.