Lower Extremity Function in Active Individuals Following ACL Reconstruction

Traditional treatment goals following anterior cruciate ligament reconstruction (ACLR) include early return to functional activity; however, the effects of recreational exercise in the presence of persistent quadriceps weakness are unknown. Without this information, it is unclear if normal short-term clinical goals are promoting long-term knee joint degeneration and predisposing the recreational athlete to premature osteoarthritis. The focus of manuscript 1 was to compare lower extremity jogging biomechanics between participants with a history of ACLR and healthy control participants as well as to compare the change in biomechanics following 30 minutes of exercise. We found that participants with a history of ACLR exhibited altered hip and knee biomechanics prior to exercise as well as knee dominant exercise adaptation strategies when compared to healthy control participants. The focus of manuscript 2 was to compare symmetry in quadriceps function between participants with a history of ACLR and healthy control participants. We found that participants with a history of ACLR exhibited greater between limb asymmetry in knee extension strength, quadriceps activation, and cortical excitability when compared to healthy control participants. The focus of manuscript 3 was to determine the clinical thresholds for knee extension strength and quadriceps activation that predicted a history of ACLR as well as positive self-reported knee function. We found that quadriceps activation symmetry below 0.996 and quadriceps strength symmetry below 0.940 were the strongest indicators of group membership. Unilateral knee extension strength above 3.75 nm/kg and quadriceps activation symmetry above 0.992 was the best indicators of positive self-reported knee related function. The combination of post-ACLR lower extremity neuromuscular asymmetry and return to full physical activity may provide important information about the rate of injury and development of OA as well as potential targets for identification and treatment of at risk individuals. Increased demand on the quadriceps throughout exercise in the presence of persistent muscle dysfunction may put those with a history of ACLR at risk for increased knee joint loading without the ability to adequately absorb forces needed to prevent long term degenerative changes.

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