The Evaluation of Postural Stability and Balance After Anterior Cruciate Ligament Reconstruction

Anterior cruciate ligament (ACL) reconstruction results in movement impairments, contributing to 20-30% of individuals sustaining a second ACL injury. One element of movement impairments that have mystified researchers up to this point is the evaluation of anticipatory and reactive postural control. Postural control requires appropriately producing coordinated muscle activity and balance throughout tasks that require a quick response. Previous literature has attempted to conduct reactive testing through cutting tests and distraction techniques. While this continues to be limited in the ability of safely evaluating subjects after ACL reconstruction, there are some techniques utilized in the literature that tests neurological impairments. Therefore, the purpose of this study is to integrate tools used in neurological conditions to evaluate postural control after ACL reconstruction through four aims. The first aim assesses anticipatory control during a submaximal knee extension force steadiness task. The second aim evaluates dynamic stability and ability to regain balance during a forward hop and a backward hop. The third aim evaluates the long latency responses of the vastus lateralis and biceps femoris during an unanticipated perturbation and the fourth evaluates how each of these previously described measures influence center of pressure stability as measured by jerk upon landing a single leg hop. These four aims will quantify different elements of postural control and will generate a research agenda to best identify and address impaired anticipatory and reactive control after ACL reconstruction.