Neuromuscular characteristics of individuals displaying excessive medial knee displacement.
BACKGROUND
Knee-valgus motion is a potential risk factor for certain lower extremity injuries, including anterior cruciate ligament injury and patellofemoral pain. Identifying neuromuscular characteristics associated with knee-valgus motion, such as hip and lower leg muscle activation, may improve our ability to prevent lower extremity injuries.


OBJECTIVE
We hypothesized that hip and lower leg muscle-activation amplitude would differ among individuals displaying knee valgus (medial knee displacement) during a double-legged squat compared with those who did not display knee valgus. We further suggested that the use of a heel lift would alter lower leg muscle activation and frontal-plane knee motion in those demonstrating medial knee displacement.


METHODS
Descriptive laboratory study.


METHODS
Research laboratory.


METHODS
A total of 37 healthy participants were assigned to the control (n = 19) or medial-knee-displacement (n = 18) group based on their double-legged squat performance.


METHODS
Muscle-activation amplitude for the gluteus maximus, gluteus medius, adductor magnus, medial and lateral gastrocnemius, and tibialis anterior was measured during 2 double-legged squat tasks. The first task consisted of performing a double-legged squat without a heel lift; the second consisted of performing a double-legged squat task with a 2-in (5.08-cm) lift under the heels.


RESULTS
Muscle-activation amplitude for the hip adductor, gastrocnemius, and tibialis anterior was greater in those who displayed knee valgus than in those who did not (P < .05). Also, use of heel lifts resulted in decreased activation of the gluteus maximus, hip adductor, gastrocnemius, and tibialis anterior muscles (P < .05). Use of heel lifts also eliminated medially directed frontal-plane knee motion in those displaying medial knee displacement.


CONCLUSIONS
Medial knee displacement during squatting tasks appears to be associated with increased hip-adductor activation and increased co-activation of the gastrocnemius and tibialis anterior muscles.
University of North Carolina at Chapel Hill, Department of Exercise and Sport Science, 216 Fetzer Gym, CB#8700, Chapel Hill, NC, USA. dpadua@email.unc.edu
Darin A
DA
Padua
David R
DR
Bell
Micheal A
MA
Clark
D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology*; D001696:Biomechanical Phenomena; D015444:Exercise; D005260:Female; D006615:Hip; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007593:Joint Instability; D007717:Knee / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture; D016059:Range of Motion, Articular; D013848:Thigh; D055815:Young Adult