Poor Static Balance is a Novel Risk Factor for Non-contact Anterior Cruciate Ligament Injury

OBJECTIVES: The anterior cruciate ligament (ACL) injury is common and affects young individuals, particularly female, who are active in sports that involve jumping, pivoting, as well as change of direction. ACL injury is associated with potential long-term complications including reduction in activity levels and osteoarthritis. In recent years, the focus on the ACL injury prevention has increased and many studies exploring risk factors for ACL injury have been published. However, the influence of the static balance on ACL injuries is poorly documented. The purpose of this study was to investigate the relationship between the static balance and incidence of ACL injury among high school female athletes. METHODS: A 3-year prospective cohort study was conducted with 287 high school female handball or basketball players. All subjects were 15 years old and included 111 handball players and 176 basketball players. At baseline, using gravicorder, postural sway was measured for 30 seconds during two-leg standing with eye open. The measured parameters of postural sway were locus length per time (LG), which indicates postural control function by proprioceptive reflexes, and environmental area (AR), which indicates the degree of equilibrium impairment. After the baseline examination was performed at high school entry, all players were followed for 36 months to register any subsequent incidence of ACL injury. We compared the differences in the static balance between injured and uninjured players using an unpaired t-test. Values of p < 0.05 were considered statistically significant. RESULTS: In the present study, 28 of the 287 players (9.6%) suffered an ACL injury during the 3-year observation period. Two players suffered both knees. Twenty five injured players sustained a non-contact injury and three injured players sustained a contact injury. Sixteen players were injured during the game and other players were injured during the practice. In this study three contact injury players were excluded. There were not significantly different between the ACL injured group and uninjured group in the stature characteristics such as age, height and weight. The mean values for LG and AR for the two-leg standing of the eye-open test were 1.30 ± 0.36 cm/s and 2.44 ± 1.34cm2 (ACL injured group), 1.15 ± 0.26 cm/s and 1.98 ± 1.02 cm2 (uninjured group). There was significantly difference between the injured group and uninjured group in LG (p = 0.045). However there was no significant difference two groups in AR (P = 0.107). (Table1) CONCLUSION: In the present study, locus length per time was significantly longer in injured players compared with uninjured players. This result showed that the postural control function by proprioceptive reflexes is the one of the risk factors for non-contact ACL injury. The proprioceptive training may be effective in ACL prevention with clinical relevance.