A Case Report of a Rare Presentation of Semimembranosus Tibial Plateau Avulsion: The Bony Ramp Lesion

Background: Tibial plateau posteromedial rim avulsions by semimembranosus tendon are a rare entity that have been reported in a few studies so far with controversial mechanisms. They are reported to accompany anterior cruciate ligament (ACL) or meniscal injuries. Their main fracture planes are usually placed in the coronal plane. Case Report: The patient was a 52-year-old man with a hyperextension-valgus tibial plateau fracture. The imaging studies revealed a compression fracture of the lateral and an avulsion fracture of the posteromedial plateau. However, no soft-tissue injuries were detected. The fragment was avulsed in the axial plane and covered by the medial meniscal posterior horn, creating the pattern of a longitudinal tear in the meniscal ramp lesion, but actually without any soft-tissue injuries. It was fixated using the tension band wiring technique with two Kirschner wires (K-wires) and one cancellous screw. Radiological and functional outcomes were excellent at 12-month follow-up. Conclusion: This fracture pattern merits special attention due to its unusual presentation, causing the meniscal posterior horn to separate from the articular surface. “Bony ramp lesion” best describes the simultaneous separation of the posterior horn of the medial meniscus (PHMM) and its underlying bony fragment without the meniscal tear that takes place in an actual medial meniscal ramp lesion.