Effects of transverse and frontal plane knee laxity on hip and knee neuromechanics during drop landings

Background: Varus-valgus (LAX VV) and internal-external (LAX IER) rotational knee laxity have received attention as potential contributing factors in anterior cruciate ligament injury. This study compared persons with above-and below-average LAX VV and LAX IER values on hip and knee neuromechanics during drop jump landings. Hypothesis: People with greater LAX VV and LAX IER values will have greater challenges controlling frontal and transverse plane knee motions, as evidenced by greater joint excursions, joint moments, and muscle activation levels during the landing phase. Study Design: Descriptive laboratory study. Methods: Recreationally active participants (52 women and 44 men) between 18 and 30 years old were measured for LAX VV and LAX IER and for their muscle activation and transverse and frontal plane hip and knee kinetics and kinematics during the initial landing phase of a drop jump. The mean value was obtained for each sex, and those with above-average values on LAX VV and LAX IER (LAX HIGH = 17 women, 16 men) were compared with those with below-average values (LAX LOW = 18 women, 17 men). Results: Women with LAX HIGH verus LAX LOW were initially positioned in greater hip adduction and knee valgus and also produced more prolonged internal hip adduction and knee varus moments as they moved toward greater hip adduction and internal rotation as the landing progressed. These patterns in LAX HIGH women were accompanied by greater prelanding and postlanding muscle activation amplitudes. Men with LAX HIGH versus LAX LOW also demonstrated greater hip adduction motion and produced greater internal hip internal rotation and knee varus and internal rotation moments. Conclusion: Participants with greater LAX VV and LAX IER landed with greater hip and knee transverse and frontal plane hip and knee motions. Clinical Relevance: People (especially, women) with increased frontal and transverse plane knee laxity demonstrate motions associated with noncontact anterior cruciate ligament injury mechanisms. © 2009 The Author(s).