Isolated Posterior Horn Medial Meniscus Bony Avulsion: A Case Report

The menisci provide mechanical stability and shock absorption in the knee joint, distributing stress across the tibial plateau. Root tears to the menisci are functionally equivalent to a total meniscectomy, frequently leading to rapidly progressive degenerative osteoarthritis within the knee joint. The majority of medial meniscal bony avulsions have been reported in younger, skeletally immature patients. Cases of bony avulsions in older patients have sparsely documented.

In this case report, we highlight the case of a 45-year-old male with a history of osteoporosis who sustained a twisting injury to the right knee which subsequently resulted in a bony avulsion injury of his medial meniscal root. MRI imaging was acquired, showing injury to the medial meniscus concurrent with an avulsion of the posterior root. A transtibial pullout repair was performed, anchoring the bony avulsion into its insertion site to allow for direct bone-to-bone healing.

This case presents a unique mechanism of injury, as most medial meniscal root injuries in older patients involve a tear of the root rather than avulsion of the bone. Additionally, meniscal bony avulsions have been reported to mainly be a consequence of acute traumatic injury. We hypothesize that this patient's history of osteoporosis contributed to his bony avulsion, especially because of his age and his relatively nontraumatic mechanism of injury.