ASYMMETRIES OF THE LOWER LIMBS AND VERTICAL JUMP LANDING PATTERNS IN DANCERS COMPARED TO NON-DANCERS AND POTENTIAL RISK OF INJURY

Dancers tend to injure the anterior cruciate ligament in their left leg more often than the right. It is unclear whether this trend is due to biased choreography or if leg dominance and left versus right asymmetries are contributing factors. The purpose of this study was to investigate asymmetries between the left and right leg, in knee abduction during landing, hip external rotation (ER) and internal rotation (IR) strength, and hip ER and IR range of motion in dancers compared to non-dancers. This study aimed to determine whether these asymmetries can be linked to leg dominance, and if this puts one leg at higher risk for ACL injury. Ten dancers and eleven non-dancers performed three maximal effort countermovement vertical jumps off of two feet, as well as three maximal effort single leg jumps on each leg. Knee abduction angles during the landing phase of the jumps were calculated using motion capture data. Maximum isometric hip ER and IR strength was measured at 15, 30, 45, 60, and 90 of knee flexion, and hip ER and IR range of motion was measured at 90 of knee flexion. Contrary to the hypothesis, few significant differences were found between the left and right leg, as well as between dancers and non-dancers. Dancers exhibited significantly greater IR range of motion than non-dancers, and knee abduction angles were greater on the right than left leg during double leg jumps. This opposes the hypothesis that knee abduction angles would be greater in dancers on the left leg. However, significant positive correlations were found
between IR strength and knee abduction angles during single leg jumps on the left leg, suggesting that IR strength may be a contributing factor to knee valgus. Further studies may want to utilize qualitative analyses, more relevant jumping tasks, and a different marker set to elucidate asymmetries of the lower limbs that may truly be present.