Angular knee jerk and fluctuation analysis for individuals with anterior cruciate ligament reconstruction and knee osteoarthritis.

Knee instability following anterior cruciate ligament (ACL) injury may accelerate knee osteoarthritis (OA) development. This study assessed knee jerk biomechanics during walking for ACL-reconstruction, knee OA, and controls. Three cohorts (1: ACL-reconstruction, 2: knee OA, and 3: healthy controls) had knee jerk quantified during a 10-meter self-selected walk. Sagittal and frontal plane jerk magnitude (peak, minimum, and range), cost (weight acceptance and full stance), and fluctuation content (mean, median, peak power frequency, and total power) were quantified and submitted to a Kruskal-Wallis H test to assess cohort differences. Magnitude and frequency of frontal, but not sagittal plane jerk was impacted by cohort. The knee OA cohort exhibited greater peak and minimum frontal plane jerk (p = 0.020 and p = 0.039), while both the ACL-reconstruction and knee OA cohorts exhibited greater range of frontal plane jerk compared to the control cohort (p = 0.001 and p = 0.028). Further, the ACL-reconstruction cohort exhibited smaller frontal plane mean frequency (p = 0.017), while both the ACL-reconstruction and knee OA cohorts had smaller peak power frequency (p = 0.020 and p = 0.041) compared to the controls. No significant difference was observed for jerk cost in the weight acceptance and full stance phase between cohorts (p = 0.124 and p = 0.107). Individuals with knee injury and disease exhibit greater frontal plane jerk magnitude with lesser fluctuation frequency indicating altered neuromuscular function at the joint that may predispose them to the development or progression of knee OA. Practitioners may need to adequately address the neuromuscular component when rehabilitating individuals with ACL injury to better facilitate short- and longer-term clinical outcomes.