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Mechanical factors have been implicated in the development of osteoarthritis after anterior cruciate ligament (ACL) reconstruction. This study tested for associations between ambulatory joint loading (total joint moment [TJM] and vertical ground reaction force [vGRF]) and changes in serum levels of cartilage oligomeric matrix protein (COMP) in response to a mechanical stimulus (30‐min walk) in individuals with ACL reconstruction. Twenty‐five subjects (mean age: 34.5 ± 9.8 years; 2.2 ± 0.2 years post‐surgery) with primary unilateral ACL reconstruction underwent gait analysis for assessment of peak vGRF and TJM first (TJM1) and second (TJM2) peaks. Serum COMP concentrations were measured by enzyme‐linked immunosorbent assay immediately before, 3.5 h, and 5.5 h after a 30‐min walk. Pearson correlation coefficients and backward stepwise multiple linear regression analysis, with adjustments for age, sex, body mass index, and between‐limb speed difference, assessed associations between changes in COMP and between‐limb differences in joint loading parameters. Greater TJM1 (R = 0.542, p = 0.005), TJM2 (R = 0.460, p = 0.021), and vGRF (R = 0.577, p = 0.003) in the ACL‐reconstructed limb as compared to the contralateral limb were associated with higher COMP values 3.5 h following the 30‐min walk. Change in COMP at 5.5 h became a significant predictor of the between‐limb difference in TJM1 and vGRF in multivariate analyses after accounting for the between‐limb speed difference. These results demonstrate that higher TJM and vGRF in the ACLR limb as compared to the contralateral limb are associated with higher relative COMP levels 3.5 and 5.5 h after a 30‐min walk. Future work should investigate the effect of therapies to alter joint loading on the biological response in individuals after ACL reconstruction. [ABSTRACT FROM AUTHOR]

Disruptions in knee biomechanics during walking following anterior cruciate ligament (ACL) injury have been suggested to lead to the development of premature knee osteoarthritis (OA) and to be potential markers of OA risk and targets for intervention. This study investigated if side‐to‐side differences in early stance peak vertical ground reaction force (vGRF) during walking 2 years after ACL reconstruction are associated with longer‐term (10 years post‐reconstruction) changes in patient‐reported outcomes. Twenty‐eight participants (mean age: 28.7 ± 6.4 years) with primary unilateral ACL reconstruction underwent gait analysis for assessment of peak vGRF and completed Knee Injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) surveys at 2 years post‐surgery (2.2 ± 0.3 years) and completed surveys at follow‐up 10 years post‐surgery (10.5 ± 0.9 years). Associations between changes (10–2 years) in patient‐reported outcomes and between limb‐differences in vGRF were assessed with Pearson or Spearman's ρ correlation coefficients and exploratory backwards elimination multiple linear regression analyses. Differences in vGRF between symptomatic progressors and non‐progressors were also assessed. The side‐to‐side difference in vGRF was related to the variability in longer‐term changes in patient‐reported outcome metrics and distinguished symptomatic progressors from non‐progressors. Participants with higher vGRF in the reconstructed (ACLR) limb versus the contralateral limb had worsening of IKDC (R = −0.391, p = 0.040), KOOS pain (ρ = −0.396, p = 0.037), KOOS symptoms (ρ = −0.572, p = 0.001), and KOOS quality of life (R = −0.458, p = 0.014) scores at follow‐up. Symptomatic progressors had greater vGRF in the ACLR limb as compared to the contralateral limb at baseline than non‐progressors (p = 0.023). These data highlight associations between a simple‐to‐measure gait metric and the development of long‐term clinical symptoms after an ACL injury. [ABSTRACT FROM AUTHOR]