Neuromuscular Characteristics of Individuals Displaying Excessive Medial Knee Displacement
Source: Journal of Athletic Training, 1 September 2012, vol. 47, no. 5, pp. 525-536(12)
Abstract:Context: 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.
Design: Descriptive laboratory study.
Setting: Research laboratory.
Patients or Other Participants: 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.
Main Outcome Measure(s): 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.
Document Type: Research Article
Affiliations: 1: University of North Carolina at Chapel Hill, Department of Exercise and Sport Science, 216 Fetzer Gym, CB#8700, Chapel Hill, NC, USA. email@example.com 2: Departments of Kinesiology and Orthopedics and Rehabilitation, University of Wisconsin–Madison School of Medicine and Public Health, USA 3: National Academy of Sports Medicine, Chandler, AZ, USA
Publication date: September 1, 2012