Acute Grade III Medial Collateral Ligament Injury of the Knee Associated with Anterior Cruciate Ligament Tear: The Usefulness of Magnetic Resonance Imaging in Determining a Treatment Regimen

Background: The appropriate management of acute grade III medial collateral ligament injury when it is combined with a torn anterior cruciate ligament has not been determined. Hypothesis: Magnetic resonance imaging grading of grade III medial collateral ligament injury in patients who also have anterior cruciate ligament injury correlates with the outcome of their nonoperative treatment. Study Design: Prospective cohort study. Methods: Seventeen patients were first treated nonoperatively with bracing. Eleven patients with restored valgus stability received anterior cruciate ligament reconstruction only, and six with residual valgus laxity also received medial collateral ligament surgery. Results: Magnetic resonance imaging depicted complete disruption of the superficial layer of the medial collateral ligament in all 17 patients and disruption of the deep layer in 14. Restoration of valgus stability was significantly correlated with the location of superficial fiber damage. Damage was evident over the whole length of the superficial layer in five patients, and all five patients had residual valgus laxity despite bracing. Both groups had good-to-excellent results 5 years later. Conclusions: Location of injury in the superficial layer may be useful in predicting the outcome of nonoperative treatment for acute grade III medial collateral ligament lesions combined with anterior cruciate ligament injury.