Postural Stability During Single-Leg Stance: A Preliminary Evaluation of Noncontact Lower Extremity Injury Risk

STUDY DESIGN: Controlled laboratory study with a prospective cohort design. BACKGROUND: Postural stability deficits during single-leg stance have been reported in persons with anterior cruciate ligament (ACL) injury, ACL reconstruction, and chronic ankle instability. It remains unclear whether impaired postural stability is a consequence or cause of these injuries. OBJECTIVES: To prospectively investigate whether postural stability deficits during single-leg stance predict noncontact lower extremity injuries. METHODS: Fifty injury-free female athletes performed a transition task from double-leg stance to single-leg stance with eyes closed. Center-of-pressure displacement, the main outcome variable, was measured during the first 3 seconds after the time to a new stability point was reached during single-leg stance. Noncontact lower extremity injuries were recorded at a 1-year follow-up. RESULTS: Six participants sustained a noncontact ACL injury or ankle sprain. Center-of-pressure displacement during the first 3 seconds after the time to a new stability point was significantly increased in the injured (P = .030) and non-injured legs (P = .009) of the injured group compared to the respective matched legs of the noninjured group. The area under the receiver operating characteristic curve (AUC) analysis revealed significant discriminative accuracy between groups for the center-of-pressure displacement during the first 3 seconds after the time to a new stability point of the injured (AUC = 0.814, P = .015) and noninjured legs (AUC -0.897, P = .004) of the injured group compared to the matched legs of the noninjured group. CONCLUSION: This preliminary study suggests that postural stability measurements during the single-leg stance phase of the double-to single-leg stance transition task may be a useful predictor of increased risk of noncontact lower extremity injury. Further research is indicated.