Summary

Patients with ACL reconstruction who had returned to sport had minimal deficits in running mechanics of the lower limb compared to an active comparison group, but demonstrated altered trunk movements.

Abstract

Successful return to sport following anterior cruciate ligament (ACL) reconstruction almost always requires that patients return to running. Despite the need for patients to attenuate high-impact forces through a single limb, little is known about the biomechanics of overground running in patients following ACL reconstruction, and particularly the movement of joints other than the knee. The aim of this study was to compare the overground running mechanics between patients who had returned to sport following anterior cruciate ligament reconstruction with that of healthy controls.

Three dimensional biomechanics were assessed in 30 participants as they ran along a 50 metre walkway at two speeds: 50% (slow) and 80% (fast) of self-determined maximum speed. Fifteen of these participants had received an anterior cruciate ligament reconstruction using hamstring autograft from a single orthopaedic surgeon at least twelve months earlier. Data was collected from at least six trials of running at each speed, and data from trials where the speed varied by more than 5% of the average were discarded. Maximum angles and moments of the ankle, knee, hip, pelvis and trunk in the sagittal plane during the stance phase of running were extracted for both the operated and non-operated limbs of the patients and for both limbs of the comparison group. These data were compared between groups using an Analysis of Covariance where body mass index and running speed were entered as covariates.

There were no differences between groups for any joint moment or angle at the ankle, knee, hip or pelvis of either the operated or non-operated limb, or at either slow or fast speeds. However, at both slow and fast speeds, the maximum forward trunk lean during stance phase of the operated limb was reduced in patients with anterior cruciate ligament reconstruction (13.7 ± 5.0 at slow speed; 14.7 ± 5.4 at fast speed) compared to controls (14.9 ± 5.8 at slow speed, p=0.047; 16.5 ± 7.2 at fast speed, p=0.008). These differences were not present during stance phase of the non-operated limb.

The findings of this study demonstrate that patients with ACL reconstruction can return to sport with minimal deficits in running mechanics compared to an active comparison group. Movement at the trunk was the only difference between groups, where ACL reconstructed patients appeared to run with a more upright trunk position. Although this difference was minimal, greater rigidity of trunk movements in dynamic tasks has been associated with increased risk of anterior cruciate ligament injury, and further investigation is necessary to understand the implications of these findings on risk of further injury.