Editorial Commentary: Combined Anterior Cruciate Ligament/Medial Collateral Ligament Injuries: Surgeons Should Have a Low Threshold to Operate on the Medial Collateral Ligament

Combined anterior cruciate ligament/medial collateral ligament (ACL/MCL) injuries are relatively common, and multiple factors are involved in surgical decision-making, particularly when it comes to the MCL. Historically, most surgeons treated the MCL conservatively and performed staged MCL reconstruction after MCL reconstruction only if there was persistent medial instability. This was followed by a nonoperative approach for the MCL (when reconstructing the ACL) unless there was evidence of extreme (grade III or >1 cm) valgus instability, valgus malalignment, or mid-substance or tibial-sided injury, avulsion, or Stener lesion. However, the most recent research demonstrates that combined ACL/MCL injuries present a higher risk of ACL reconstruction failure and subsequent revision compared to ACL injuries alone. With growing biomechanical and clinical evidence, more surgeons are repairing or reconstructing the MCL in these combined injuries. Although there is no clear consensus, we recommend surgeons consider surgically treating the MCL to avoid not only excessive force on the ACL graft but also persistent valgus laxity, which can lead to ACL failure. For distal MCL avulsions, repairs have shown excellent midterm outcomes, especially if the tissue quality is pristine. If the tissue quality is not repairable, then we would advocate for repairing whatever tissue is repairable and augmenting with an MCL reconstruction. For mid-substance MCL injuries, if surgical intervention is required, we advocate for MCL reconstruction. For proximal tears, the same criteria used for distal tears apply with management based on tissue quality and joint stability after repair. The ACL is a secondary stabilizer to valgus loads, and MCL deficiency results in tremendous strain on ACL graft reconstructions. If the MCL is even mildly incompetent, we strongly advocate for treating the MCL surgically in this setting.