Research-Based and Clinical Considerations for Effective Neuromuscular Training to Prevent Second Anterior Cruciate Ligament Injury

The second anterior cruciate ligament (ACL) injury after ACL reconstruction occurs at reported rates, ranging from 5-20 times greater than that of the primary injury, and results in significantly poorer patient outcomes. In athletes, most of the second ACL injuries occur within the first 2 years of return to sport. Significant functional impairments and deficits in neuromuscular control are frequently reported up to 2 years postreconstruction. Neuromuscular deficit-targeted neuromuscular training (NMT) alters high-risk biomechanics and reduces rates of primary ACL injury. Its efficacy in ACL-injured subjects is currently unknown. External loads during dynamic motion, specifically knee abduction moment, internal tibial rotation moment, and proximal anterior tibial shear force, especially in the lateral compartment, increase ACL strain. These factors are reportedly influenced by modifiable and nonmodifiable factors. ACL reconstruction subjects pose a unique challenge to clinicians and researchers due to the numerous confounding factors in identifying and addressing their risk of reinjury. However, they also may provide clinicians and researchers with a great deal of accessible, highly pertinent clinical, anatomical, and biomechanical information in the forms of medical images, charts, and rehabilitation notes. Thorough determination of postoperative biomechanical impairments, modifiable and nonmodifiable risk factors, and the effects of NMT on these factors aids in eventual reduction of second ACL injury rates. A properly structured and executed large-scale, multicenter trial to evaluate the biomechanical efficacy of NMT in the context of these factors would be invaluable both clinically and academically.