Abstract
Quadriceps strength deficits persist for years following ACL reconstruction and are an important determinant of performance and self-reported outcomes. During functional tasks, patients often shift torque demands away from the knee extensors to the hip. However, it is not clear if hip strength is altered as a result of these demands. PURPOSE: To determine if quadriceps strength asymmetry influences hip muscle strength in ACL reconstructed patients. METHODS: Fifty-five patients with a history of primary, unilateral ACLR volunteered for this study. Isometric strength measurements were recorded bilaterally from the quadriceps, hamstrings, hip extensors, hip abductors, hip internal, and external rotator muscle groups. Single hop for distance (SHD) normalized to leg length was completed along with IKDC knee function scale. Patients were grouped based on between limb quadriceps strength symmetry of reconstructed and healthy limbs (Limb Symmetry Index (LSI) = involved/healthy*100). The High Quad (F = 31, M = 6; age = 19.1 ± 1.7yrs, months from surgery = 34.9 ± 19.0) had a LSI≥90%, whereas the Low Quad (F = 17, M = 1; age = 18.7 ± 1.6yrs; months from surgery=2.6±10.6) demonstrated a LSI≤85%. Group (High Quad vs Low Quad LSI) by Limb (injured vs healthy) RMANOVAs compared strength values in each muscle group. ANOVAs were used to compare SHD LSI and IKDC scores. All analyses controlled for time from surgery (p≤.05). RESULTS: Groups did not differ between SHD LSI (High Quad LSI: 97.8 ± 7.2%; Low Quad LSI: 95.2 ± 6.3%, P = .30) and IKDC scores (High Quad LSI: 84.58 ± 9.15%; Low Quad LSI: 86.63 ± 7.83%, P=.38). A group main effect was observed for the hip extensors with the Low LSI (.48±.12 %BW) being stronger than the High LSI group (.38±.14%BW, P=.02). Hip abduction strength tended to differ between groups (High LSI: .43±.09%BW, Low LSI: .49±.11%BW, P=.051). No other significant differences were observed (P>.05). CONCLUSION: ACLR individuals with poor between limb quadriceps strength symmetry have increased hip extensor (glute max) and abductor (glute medius) strength. This is most likely a compensation to counteract quadriceps weakness by shifting muscular demands away from the knee to the hip. These compensations may explain why SHD and knee function was not different. Supported by Sports Medicine Classic and UW Graduate School
Published Version
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