Background ACL injury rate for female is as much as eight times higher than male in the United States. However, based upon Korean Health Insurance Corporation, higher injury rate was reported in male compared to female.

Objective To determine whether ethnic differences exist in lower extremity dynamic postural measures between Caucasian female and Asian female.

Design Case controlled study.

Setting Controlled laboratory.

Patients (or Participants) 15 Caucasian female (age: 21.3±1.58 yrs; weight: 63.9±7.42 kg; height: 169.6±4.60 cm) and 15 Asian female (age: 20.4±1.20 yrs; weight: 57.8±3.86 kg; height: 164.0±2.72 cm) were recruited as subjects for this study.

Interventions (or Assessment of Risk Factors) All subjects performed Drop jump from a 30 cm-box, which was set at the half of their height distance away from the force plate.

Main Outcome Measurements Three dimensional knee joint kinematics were extracted from motion analysis system (Vicon Inc, Oxford, UK; BTS Bioengineering, Milano, Italy). All joint kinematics were analyzed at one discrete point which was 30° knee flexion. Independent sample t-test was performed to analyze mean differences between ethnicity.

Results Caucasian female had significantly greater knee valgus (t=−3.293, p=0.03, Caucasian: −3.15°±6.12°; Asian: 3.19°±3.94°) and knee internal rotation (t=2.143, p=0.41, Caucasian: 12.58°±9.54°; Asian: 5.05°±9.35°) compared to Asian female in Drop jump.

Conclusions Our results showing significantly greater knee valgus and internal rotation in Caucasian female may support the difference of ACL injury rates between Caucasian and Asian. Possibly reducing knee valgus and internal rotation may drop the injury rate of female to similar with male as found in South Korea.