Knee Abduction Angle and Notch Width are Potential Factors Related to Familial Predisposition to Anterior Cruciate Ligament Injury

Abstract

PURPOSE: Knee abduction during landing is a potential predictor of anterior cruciate ligament (ACL) injury risk in female athletes (Hewett et al. 2005). Femoral notch width may also predict ACL injury risk in females. Studies of twin siblings yield important information regarding genetic traits and predisposition to disease or injury. The objective was to determine if prescreened twin female athletes demonstrate risk factors of increased knee abduction angle and decreased femoral notch width. Quantification of these potential traits may lead to identification of familial predisposition of ACL injury. METHODS: Fraternal twin female athletes in high-risk sports of soccer and basketball were prospectively measured for neuromuscular control using 3-dimensional kinematics (knee joint angles) during jump landing. Intraoperative measures of femoral notch width were also recorded during ACL reconstruction. Knee joint angle and femoral notch width were compared to a tested population of knees of uninjured female athletes in the same high-risk sports (390 knees total) to isolate risk in the twin group. RESULTS: Knee abduction angles were greater than one standard deviation (SD) above the mean in the twin sister (female) athletes relative to the uninjured group of female athletes both at initial contact and at maximum displacement during landing. The twin female athletes that went on to ACL injury had 7.8 and 9.7 degrees greater knee abduction at initial contact and maximum angle than in uninjured female athletes during landing. Femoral notch widths were approximately one SD below the mean in the twins relative to uninjured females. The twin sisters had notch widths 2.5 to 3.5 mm lower than controls. CONCLUSIONS: The prescreened twin female athletes that suffered ACL injury demonstrated potential risk factors of both increased knee abduction angle and decreased femoral notch width. Increased knee abduction angle and decreased notch widths are potential traits related to familial predisposition of ACL injury.