Fabella Syndrome Following De-Rotation Surgery to Correct a Femoral Malunion

Background:The fabella is a sesamoid bone situated within the lateral head of the gastrocnemius tendon, close to the lateral femoral condyle, and adjoined to the fabellofibular ligament. It is a normal variant, found in up to 87% of patients. Fabella Syndrome describes traditionally posterolateral knee pain, occurring due to biomechanical pressure of the fabella against the lateral femoral condyle. Given its rarity, its diagnosis is often overlooked. We present a case of Fabella Syndrome with a modified surgical excision technique and review of the literature.Methods and Results:A thirty-four-year-old man presented with posterolateral knee pain following de-rotation surgery to correct a femoral malunion, from a previous femoral shaft fracture. Due to the patient’s complex orthopaedic history, Fabella Syndrome was not initially diagnosed. Fabellectomy eliminated all symptoms of knee pain, with no limitations in knee function.Conclusion:Review of the literature identified ten publications (evidence level IV) describing Fabella Syndrome. This is the first reported case of Fabella Syndrome secondary to femoral de-rotation surgery. The authors recommend fabellectomy as a definitive treatment for Fabella Syndrome, in keeping with published literature.