No shortage of disagreement between biomechanical and clinical hop symmetry after anterior cruciate ligament reconstruction

Background: Evaluating average performance on functional hop tasks can potentially overestimate physical function, as it masks variability present within individual trials and may lead to clinician oversight regarding the overall movement quality. The purpose was to evaluate the trial-by-trial agreement between hop-distance symmetry and knee biomechanics (knee flexion angle, knee extension moment) to reveal the full extent of agreement between these measures.

Methods: Sixteen individuals with primary, unilateral anterior cruciate ligament reconstruction participated (age: 22(2) y; height: 1.71(0.11) m; mass: 68.94(13.06) kg; gender: 8 males, 8 females; years' post-surgery:4(3) y) in a cross-sectional study. Knee kinematics and kinetics were measured using 3D motion analysis and hop distance was collected during the triple hop for distance. Individual limb difference values for individual hop trials were calculated and values for each trial were dichotomized as pass/fail based on achieving a limb difference of <10%. Cohen's Kappa and confirmatory McNemar's test were performed to determine the level of agreement between measures of physical and biomechanical function between trials.

Findings: No agreement between triple hop and peak knee flexion angle symmetry (κ = 0.033, p = 0.387) and peak internal knee extension moment (κ = 0.022, p = 0.475) were found. McNemar tests confirmed no agreement between hop-distance %LD and knee flexion angle/knee extension moment %LD (p = 0.000).

Interpretation: These findings suggest that while individuals after ACLR may on average achieve symmetrical hop-distance, they may not necessarily pass subsequent functional tasks. Further, individual trial-by-trial analyses may provide insight into an individual's true physical capability compared to simply evaluating the average, which may overestimate physical function or mask altered movement strategies.