Lower Extremity Mechanical Energetics During Walking 6 Months Following Anterior Cruciate Ligament Reconstruction.

Aberrant gait biomechanics following anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) are critical factors contributing to the development of knee osteoarthritis (KOA). However, it remains unknown how ACLR impacts lower extremity joint energetics and each joint's contribution to total limb energetics during walking. To compare mechanical energetics at the ankle, knee, and hip joints between ACLR limbs, contralateral, and control limbs during walking. Forty-four participants with primary unilateral ACLR (post-ACLR: 6.0 ± 0.2 months) and 44 uninjured controls were studied. Ankle, knee, and hip joint work were calculated as the time integral of the negative (energy dissipation) or positive (energy generation) regions of the respective stance-phase joint power curves. The joint-specific contribution to total limb energy dissipation and generation was calculated. ANCOVA was used to assess differences in energy dissipation and generation at the ankle, knee, and hip between ACLR, contralateral, and matched control limbs, respectively. Compared to contralateral and matched control limbs, ACLR limbs exhibited lesser energy dissipation (ACLR: -0.06 ± 0.03 J/kg; vs. contralateral: -0.12 ± 0.07; vs. control: -0.12 ± 0.04; p < 0.001, all) and generation (0.08 ± 0.03 vs. 0.11 ± 0.06 vs. 0.10 ± 0.04; p < 0.001, all) about the knee joint and lesser contribution from the knee (66.8 ± 33.0 vs. 79.8 ± 26.7 vs. 79.9 ± 23.1; p = 0.01, all) and greater contribution from the hip (30.5 ± 33.1 vs. 14.5 ± 23.5 vs. 14.7 ± 19.8; p = 0.004 and p = 0.003, respectively) to total limb generation during mid-stance. Compared to contralateral limbs and matched controls, individuals at 6 months post ACLR exhibit altered lower extremity mechanical energetics, with decreased knee contributions and a greater hip contribution during walking.