Lower Extremity Compensatory Neuromuscular and Biomechanical Adaptations 2 to 11 Years After Anterior Cruciate Ligament Reconstruction

PurposeTo determine whether compensatory neuromuscular and biomechanical adaptations exist after successful anterior cruciate ligament reconstruction and rehabilitation.MethodsSeventy subjects, 5.3 ± 3 years after surgery, participated in this study. Sagittal-plane lower extremity kinematic, gluteus maximus, vastus medialis, medial hamstring, and gastrocnemius electromyography (EMG) and vertical ground reaction force data were collected during single-leg countermovement jump (CMJ) performance.ResultsWomen had lower propulsive and landing forces, lower CMJ heights, less hip and knee flexion, and greater angular hip, knee, and ankle velocities than men (P ≤ .014). The involved lower extremity of men and women had decreased landing forces (P = .008). During propulsion, men and women had increased involved–lower extremity gluteus maximus (P < .0001) and decreased vastus medialis (P = .013) EMG amplitudes, whereas women had bilaterally increased gastrocnemius EMG amplitudes compared with men (P = .003). During propulsion, men had longer gluteus maximus and vastus medialis EMG durations than women (P < .0001). During landing, both men and women had increased gluteus maximus EMG amplitudes at the involved lower extremity (P < .0001). Women had increased vastus medialis (P = .01) and gastrocnemius (P < .0001) EMG amplitudes compared with men. During landing, men had longer gluteus maximus (P = .004), vastus medialis (P = .012), and gastrocnemius (P = .007) EMG durations than women and the involved–lower extremity vastus medialis EMG durations of both men and women were shorter than at the noninvolved lower extremity (P = .011).ConclusionsDecreased involved–lower extremity landing forces, decreased vastus medialis activation, and increased gluteus maximus and gastrocnemius activation suggest a protective mechanism to minimize knee loads that increase anterior translatory knee forces during single-leg jumping. Women showed more balanced gluteus maximus, vastus medialis, and gastrocnemius contributions to dynamic knee stability than men during CMJ landings but used shorter activation durations.Level of EvidenceLevel IV, therapeutic case series.