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ABSTRACT
Gluteal musculature weakness is associated with lower extremity injury and greater frontal plane knee motion. A method for functionally evaluating hip abduction and external rotation strength by observing knee motion would be beneficial for clinicians. This study evaluated the association between hip abductor and external rotation strength and knee motion. Peak isometric and eccentric hip abduction and external rotation strength were assessed in 47 healthy participants before analysis of knee kinematics during a lateral step-down test. The relationships between each strength measure and frontal plane knee kinematics were evaluated using bivariate Pearson correlation coefficients. Frontal plane knee displacement was not associated with hip musculature strength. Frontal plane knee angle at peak knee flexion was not associated with external rotation or eccentric abduction strength. Isometric abduction strength was negatively correlated with peak knee flexion. Hip musculature strength is not indicative of the magnitude of frontal plane knee motion during the lateral step-down test, and this test is not recommended for clinical assessment of hip muscle strength.
Weakness of the hip abductors and external rotators is associated with a variety of lower extremity injuries as well as low back pain.1-5 Specifically, decreased hip abduction and external rotation strength has been reported in individuals with patellofemoral pain syndrome,1,3,5 whereas lesser hip abductor strength has been observed in patients with iliotibial band friction syndrome.2 Furthermore, a prospective evaluation of collegiate athletes found individuals who suffered a lower extremity or low back injury displayed lesser hip abduction and external rotation strength compared to their uninjured counterparts.4
In addition to strength deficits, a lower extremity kinematic pattern consisting of hip adduction and internal rotation, and knee valgus has been proposed as a risk factor for patellofemoral pain syndrome,3,6,7 iliotibial band friction syndrome,2 and anterior cruciate ligament injury.8,9 As a result, it has been suggested that greater eccentric resistance to hip adduction and internal rotation provided by the hip abductors and external rotators may attenuate this kinematic pattern and result in an associated decrease in knee valgus.2,3,10 This premise is supported by studies reporting greater frontal plane knee motion during running11 and single-leg landing10 in individuals with weak hip musculature. Accordingly, it has been recommended that rehabilitation and prevention programs for these injuries should include evaluation and strengthening of the...