Lower Extremity Kinetic and Kinematic Asymmetries 4, 6, and 9 Months Post-ACL Reconstruction In Elite Collegiate Athletes

Abstract

Abnormal lower extremity (LE) biomechanics post-anterior cruciate ligament reconstruction (ACLR) may increase re-injury risk and reduce sports performance. Although most athletes return to sport (RTS) within 1 year from ACLR, the timeline for recovery of LE kinetics and kinematics during athletic tasks is not well defined. Identifying specific movement deficiencies will guide rehabilitation efforts to promote successful RTS and reduce re-injury risk. PURPOSE: To evaluate vertical ground reaction forces (vGRF) and hip, knee, and ankle kinematics during running and jumping in elite collegiate athletes 4, 6, and 9 months post-ACLR. METHODS: Twelve Division I athletes (age 20.5 ± 1.2, BMI 25.9 ± 3.6, 6 female) performed maximal countermovement jumps (CMJ) and treadmill running at a maximally comfortable speed 4.0 ± 0.3, 6.1 ± 0.5 and 8.9 ± 1.5 months post-surgery while whole body kinematics were recorded. VGRF impulses, knee flexion excursion, and peak sagittal plane hip, knee, and ankle joint angles were obtained during the stance phase of running (RUN) and the eccentric, concentric (CON), and landing (LAND) phases of the CMJ. Limb symmetry indices (LSI) were computed for all variables and effect sizes (ES) were calculated. LSIs at each interval were evaluated using the Wilcoxon Signed-Ranks test. RESULTS: At 4 months post-surgery, all CMJ and RUN asymmetries were significant (LSI: 69.5-95.9%, p < .023, ES: .46-.62). Involved limb CMJ CONC phase and RUN vGRF impulses were significantly less than uninvolved limb values at all intervals (LSI: 85.7-94.2%, p < .005, ES: .58-.63). RUN peak joint angle and knee flexion excursion asymmetries were significant at all intervals (LSI: 69.5-94.7%, p < .013, ES: .51-.62). Involved limb CMJ CONC phase knee (LSI: 90.6-98.6%, p < .041, ES: .42-.62) and ankle (LSI: 80.2-86.1%, p < .010, ES: .53-.62) angles were reduced throughout, while no CMJ LAND phase asymmetries were detected 9 months post-op. CONCLUSIONS: Despite excellent surgical care and high volumes of rehabilitation, elite collegiate athletes present with LE kinetic and kinematic asymmetries 9 months post-surgery, after or close to typical RTS. In particular, knee joint kinematics during the stance phase of running and the CONC phase of the CMJ are categorically asymmetric and should be addressed with targeted interventions.