Tibial Avulsion with Intra-Articular Entrapment of Medial Collateral Ligament with Posterior Cruciate Ligament Tear with Posterior Root Medial Meniscus Tear: A Case Report of an Unusual Injury Triad

INTRODUCTION: The medial collateral ligament (MCL) is the most commonly injured ligament of the knee joint; however, its displacement into the medial knee compartment is rare. Traumatic posterior root of medial meniscus (PRMM) tears are commonly found in high-grade injuries involving anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) tears along with MCL tears. Diagnosis of these injuries can be made by a preoperative magnetic resonance imaging (MRI), but they can be missed at times due to severe soft-tissue swelling in the acute phase. CASE REPORT: A 25-year-old gentleman presented with injury to the front of his left knee 5 days back. On examination, he had a Grade 3 effusion with valgus stress test and posterior drawer test being positive and medial joint line tenderness was present. A firm localized swelling was palpable on the medial joint line. MRI scan revealed a mid-substance PCL tear, ACL sprain, PRMM tear, and tibial side rupture of superficial MCL with proximally migrated wavy MCL fibers lying below the medial meniscus confirmed on arthroscopy. Medial meniscus root repair by pull through technique and PCL reconstruction with a 3-strand peroneus longus graft followed by open MCL repair with augmentation using a semitendinosus graft was performed. Postoperatively, the knee was kept in a straight knee brace for 4 weeks, followed by a hinged knee brace and appropriate physiotherapy were started. At 2 years follow-up, the patient had attained full range of knee motion with good quadriceps strength, tibial step off maintained, and negative posterior drawer test and valgus stress test. Displacement of torn MCL into the medial knee compartment is an extremely rare injury. Proximal or distal avulsion of MCL with intra-articular incarceration has been reported in isolation or associated with ACL tear. Such an injury triad as reported here has not been reported in the literature to the best of our review. CONCLUSION: In our case, we report a very unusual injury triad of PCL tear, PRMM tear, and distal MCL tear with intra-articular entrapment below the medial meniscus operated by a single-stage surgery with excellent outcomes.