Intra-articular entrapment of the medial collateral ligament

The medial collateral ligament (MCL) is the most commonly injured knee ligament. Such injuries in children are rare due to the relative thickness of the articular cartilage and physes that can absorb energy. Traumatic MCL entrapment into the medial knee joint in a child has not yet been reported. This article presents a case of intra-articular MCL entrapment in a 9-year-old boy with characteristic findings on magnetic resonance imaging (MRI) showing the interposition of the MCL between the medial meniscus and medial tibial plateau. During arthroscopic surgery, the MCL tear pattern was visualized underneath the medial meniscus. A medial knee incision was performed and the MCL was retrieved from the knee joint. The meniscotibial ligaments and medial meniscus were repaired to the tibial plateau. The torn ends of MCL were reapproximated and sutured. One year postoperatively, the patient is back to full activities including sports without limitations. This article should help raise awareness about the possibility of such injuries to avoid a delay in diagnosis. Although it is true that children would injure their physes more often than their ligaments due to their relative weakness, this article describes the possibility of a serious ligament injury without physeal involvement.