Perception of symmetry and asymmetry in individuals with anterior cruciate ligament reconstruction.

Background: Changes in the quantity, quality and integration of sensory information are thought to persist long after anterior cruciate ligament reconstruction and completion of physical therapy. Our purpose was to investigate the ability of individuals with anterior cruciate ligament reconstruction to perceive imposed asymmetry and symmetry while walking.

Methods: Twenty participants with anterior cruciate ligament reconstruction and 20 controls walked on a split-belt treadmill while we assessed the ability to detect symmetry and asymmetry at fast and slow speeds. Detection scores and spatiotemporal data during asymmetric and symmetric tasks in which the belts were coupled or decoupled over time were recorded.

Findings: The ability to detect symmetry and asymmetry was not altered in individuals with anterior cruciate ligament reconstruction compared to healthy young adults. The belt-speed ratio at detection also correlated to asymmetry for step length, stride length, double support time, and stance time. However, the anterior cruciate ligament reconstruction group appeared to utilize unique information to determine detection. When asked to detect symmetry at a fast speed, no asymmetry scores significantly correlated with belt-speed ratio in the anterior cruciate ligament reconstruction group. Conversely, asymmetry in stride length, step length, and stance time all significantly correlated with belt-speed ratio at detection in the control group.

Interpretation: Specific sensory cues arising from the speed of the leg may also augment perception of symmetry. This strategy may be necessary in order to successfully execute the motor task, and could develop due to altered sensory information from the reconstructed knee at faster walking speeds.