Background: A discrepancy in the incidence of anterior cruciate ligament injury in males and females appears after puberty; however, little is known about changes that occur in control of the lower limbs during jump-landing in adolescents.
Methods: Twenty-five male and 29 female 5th grade students (age 10-11 years) participated at the beginning of study and were followed for 5 consecutive years. Control of the lower limbs during jump-landing was evaluated by use of a drop-jump test and 2-dimensional video analysis. The K/H ratio, which was determined by dividing the knee-separation distance by the hip-separation distance, was calculated for initial contact (IC) and for maximum knee flexion (MKF).
Results: In all grades female subjects had a significantly lower K/H ratio at both IC and MKF than male subjects. Although no statistically significant difference in K/H ratio between age categories was shown at either IC or MKF for male subjects, K/H ratio at IC and MKF decreased significantly between 5th grade and 9th grade for female subjects.
Conclusion: This study suggests that adolescent females have a lower K/H ratio during jump-landing than male subjects of the same age, and that K/H ratio for females decreases with increasing age.