The following is a summary of the “Patellofemoral contact forces and knee gait mechanics 3 months after ACL reconstruction are associated with cartilage degradation 24 months after surgery,” published in the February 2023 issue of Osteoarthritis and Cartilage by Williams, et al.

Examine the relationship between patellofemoral contact forces and knee mechanics during gait 3 months after ACL reconstruction (ACLR) and patellofemoral cartilage health, as determined by qMRI T2 relaxation times, 24 months after ACLR. Mostly 3 months following ACLR, 30 participants underwent motion analysis while walking overground at their own pace. The muscle forces were calculated using an EMG-driven neuromusculoskeletal model and then incorporated into a previously reported model to estimate patellofemoral contact forces. Peak patellofemoral contact force, peak knee flexion angle, and peak knee flexion moment were among the biomechanical factors examined. 

Nearly 24 months following surgery, these same people had a sagittal bilateral T2 mapping quantitative magnetic resonance imaging scan. Patellar and trochlear cartilage T2 relaxation durations were estimated. When comparing T2 relaxation times between limbs, paired t-tests were used, whereas Pearson correlations and linear regressions were used to analyze the relationship between the biomechanical factors of interest and T2 relaxation times. 24 months following surgery, trochlear T2 relaxation periods were longer in the operated limb compared to the unoperated limb, indicating poorer cartilage health.

The patellar cartilage showed no signs of variation. At 3 months following ACLR and 24 months later, trochlear T2 relaxation times were negatively correlated with all biomechanical characteristics of interest within the affected limb. The patellar cartilage and the uninvolved limb both tested negative for links. Nearly 24 months after ACLR, trochlear cartilage health in the affected limb is altered, possibly related to patellofemoral loading and other walking gait mechanics as early as 3 months after surgery.