Recovery Of Preinjury Walking Biomechanics Following Anterior Cruciate Ligament Reconstruction In Division I Collegiate Athletes

Altered involved (INV) knee joint walking mechanics following anterior cruciate ligament reconstruction (ACLR) are well documented. Typically, the uninvolved limb (UNI) is used as a healthy comparison. However, bilateral impairments can occur post-ACLR, which could contribute to misrepresentation of the recovery of gait mechanics. Preinjury (PRE) walking mechanics, though rarely available, offer an ideal reference to characterize post-ACLR changes in both limbs. PURPOSE: Assess INV, UNI, and between limb changes in walking mechanics from PRE to 17-months post-ACLR. METHODS: Division I collegiate athletes (n = 23; 12 Female; age: 20.5 ± 1.5) walked on a treadmill (1.2 m/s) while kinematics and ground reaction forces (GRF) were collected at PRE, 4, 6, 8, 12 and 17 months (M) post-ACLR, with 23, 12, 17, 12, 12, and 5 observations, respectively. Peak vertical GRF (vGRF), knee flexion excursion (KFE) and peak knee extensor moments (PKEM) during stance were variables of interest. Linear mixed effects models assessed changes in mechanics from PRE within and between each limb with time, limb, and a time*limb interaction as fixed effects and athlete and limb as random effects. Least square mean differences ± standard error and associated Tukey-adjusted p-values are reported. RESULTS: Time*limb interactions were significant for vGRF (p = 0.02), KFE (p < 0.001), and PKEM (p = 0.01). INV KFE decreased at 4 M (5.9° ± 1.1, p < 0.01) and 6 M (5.3° ± 0.9, p < 0.01), recovered to PRE by 8 M (3.5° ± 1.1, p = 0.06), and remained similar to PRE at 12 M and 17 M. Compared to PRE, no significant INV deficits (all p-values>0.05) were observed for vGRF (range: -0.25 ± 0.10, -2.4% [4 M] to 0.02 ± 0.10 N/kg, 0.2% [8 M]) or PKEM (range: -0.08 ± 0.04, -23% [4 M] to 0.02 ± 0.04 Nm/kg, 5.8% [8 M]). No significant UNI changes from PRE were observed for all metrics (all p-values>0.05). INV KFE was less than UNI at 4 M (5.7° ± 1.3, p < 0.01) and 6 M (5.4° ± 1.1, p < 0.01). CONCLUSION: INV KFE during walking is reduced at 4 M and 6 M post-ACLR compared to PRE and UNI. UNI appears to be a valid reference for recovery of INV walking mechanics given minimal changes from PRE. Although INV vGRF and PKEM showed similar trends over time, changes from PRE were not statistically significant. Assessing gait mechanics on an individual basis is likely needed, given the significant variation in INV mechanics.