Altered Knee Biomechanics Persist In Females Who Have Undergone ACL Reconstruction Using An Allograft

Rupture of the anterior cruciate ligament is a common injury experienced by females who participate in sport. Altered knee biomechanics (i.e., decreased knee flexion, increased muscle co-contraction) have been reported in individuals following anterior cruciate ligament reconstruction (ACLR). These studies however, only evaluated knees that had been reconstructed using patella or hamstring tendon autografts. Whether individuals who have undergone an ACLR procedure using an allograft demonstrate altered knee biomechanics remains to be seen. PURPOSE: To examine knee mechanics in females following ACLR using an allograft. METHODS: Eight females with unilateral ACLR that used an allograft and 8 matched healthy controls participated. The average time from surgery in the ACLR group was 28.0 ± 14.3 months. ACRL subjects had completed rehabilitation and had been cleared to return to full activity by the orthopaedic surgeon. Knee kinematics (8-camera motion system), kinetics (force platform), and muscle activation (surface EMG) of the quadriceps and hamstrings were recorded while subjects performed a single-leg drop-land task. Peak knee joint angles, peak net knee joint moments (normalized to body mass and leg length), and the co-contraction index (CCI) of the hamstrings and quadriceps during the deceleration phase of landing were calculated. Differences between the 2 groups were examined using independent t-tests. RESULTS: Peak knee flexion angles in the ACLR group were significantly less than the control group (68.4 ± 12.0° vs. 79.4 ± 12.6°, p = 0.049). When compared to the control group, the ACLR group also demonstrated a significantly greater CCI (0.30 ± 0.16 vs. 0.15 ± 0.05, p = 0.019). Although not statistically significant, the ACLR group showed a trend toward a significantly smaller peak knee extensor moments when compared to the control group (3.0 ± 0.6 vs. 3.4 ± 0.4 Nm·kg-1·m-1, p = 0.067). CONCLUSIONS: Females who have undergone ACLR using an allograft continue to demonstrate altered knee biomechanics post-rehabilitation. Our findings are similar to what has been reported previously in individuals who have undergone ACLR using an autograft. Our findings suggest that biomechanical function following ACLR may be independent of the procedure used to reconstruct the anterior cruciate ligament.