Patellofemoral Joint Loading and Early Osteoarthritis After ACL Reconstruction Summary Osteoarthritis of the patellofemoral joint (PFJ) is common after anterior cruciate ligament reconstruction (ACLR) and may be related to altered joint loading . However, little is known about the cross-sectional and longitudinal relationship between PFJ loading and post-ACLR osteoarthritis. This study evaluated whether altered PFJ loading is associated with the prevalence and worsening of early PFJ osteoarthritis after ACLR. Forty-six participants (mean ± 1 SD age 26 ± 5 years) approximately 1 year after ACLR underwent magnetic resonance imaging (MRI) and biomechanical evaluation of their reconstructed knee. Trunk and lower extremity kinematics plus ground reaction forces were recorded during the landing phase of a standardized forward jump. These data were input into a musculoskeletal model to calculate PFJ contact force. Follow-up MRI was completed in 32 participants at 5 years post-ACLR. Generalized linear models (Poisson regression) assessed the relationship between PFJ burden and prevalent early PFJ osteoarthritis (i.e., presence of a PFJ cartilage lesion 1 year after ACLR) and worsening of PFJ osteoarthritis. PFJ (i.e., incident/progressive PFJ cartilage injury between 1 - and 5 years post-ACLR). Lower peak PFJ contact force was associated with prevalent early PFJ osteoarthritis at 1 year post-ACLR (n = 14 [30.4%]; prevalence ratio: 1.37; 95% confidence interval [CI] %: 1.02–1.85) and an increased risk of worsening PFJ osteoarthritis 1 to 5 years after ACLR (n = 9 [28.1%]; hazard ratio: 1.55, CI 1.02–1.85) 95%: 1.13–2.11). Young adults after ACLR who exhibited lower PFJ loading during jumping were more likely to have early PFJ osteoarthritis at 1 year and worsening PFJ osteoarthritis between 1 and 5 years. Clinical interventions aimed at mitigating osteoarthritis progression may be beneficial for those with signs of reduced PFJ loading after anterior cruciate ligament reconstruction (ACLR) . |
Time series plot illustrating patellofemoral joint contact force during the landing phase of a standardized forward jump task for the 32 participants involved in the longitudinal analysis. The y-axis indicates the magnitude of the patellofemoral joint contact force normalized to the body weight (BW) of each participant. The x-axis indicates the normalized time from 0% to 100% of the landing phase. Top panel (A): Solid blue line represents the group mean curve for the 23 participants without worsening patellofemoral joint osteoarthritis (PFJOA no worsening); the red dashed line represents the group mean curve for the nine participants with worsening patellofemoral joint osteoarthritis (worsening PFJOA). Bottom panel (B): Solid blue line represents the 18 participants without early patellofemoral joint osteoarthritis at any of the time points (no early PFJOA at 1 or 5 years); the dashed gray line represents the five participants with early PFJOA at 1 year after ACL reconstruction that did not worsen between 1 and 5 years (early PFJOA at 1 year but no worsening); the red dashed line represents the group mean curve for the nine participants with worsening patellofemoral joint osteoarthritis (worsening PFJOA). Shaded regions in both panels represent the variability (±1 SD) of patellofemoral joint contact force for each group. PFJOA, patellofemoral joint osteoarthritis
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Arthritis in the patellofemoral (PFJ) joint of the knee is common after anterior cruciate ligament reconstruction (ACLR) and may be related to altered loading or stress on the joint. In a study published in the Journal of Orthopedic Research , young adults after ACLR who exhibited lower PFJ loading during jumping were more likely to have PFJ osteoarthritis at 1 year and worsening PFJ osteoarthritis between 1 and 5 years .
In the study, PFJ net contact force data were normalized to each participant’s body weight. For each body weight decrease in maximum PFJ contact force during jumping, the proportion of people 1 year after ACLR with early PFJ osteoarthritis increased by 37%, and the risk of worsening PFJ osteoarthritis among 1 and 5 years later. -ACLR increased by 55%.
“Clinical interventions aimed at mitigating osteoarthritis progression may be beneficial for those with signs of reduced PFJ burden after ACLR,” the authors wrote.
In conclusion , young adults after ACLR who exhibited lower PFJ load during jumping were more likely to have early PFJOA at 1 year and worsening PFJOA between 1 and 5 years. Monitoring PFJ loading indices during relevant functional tasks as soon as possible after ACLR could represent an opportunity to identify those at highest risk of developing end-stage PFJOA. Future studies involving a larger cohort and examining changes in structural degradation over a longer period are needed to corroborate our findings.
