A Avulsion Fracture of the Lateral Patellofemoral Ligament: A Rare Case Report

Abstract

We present the case of an adolescent with anterior knee pain after a sprint, without history of knee trauma or surgery, diagnosed with a lateral patellofemoral retinaculum avulsion fracture. Signs of Osgood–Schlatter disease were also present. Radiography revealed a small calcific fragment adjacent to the lateral patellar border, while MRI confirmed lateral patellar bone marrow edema, retinacular thickening and periosteal avulsion. Additional findings included bone marrow edema of the medial femoral condyle, which is suggestive of a transient medial patellar dislocation, even though the patient didn’t recall any traumatic event. Avulsions at the lateral retinacular insertion are extremely rare, with most reports focusing on iatrogenic medial instability. Recognition of this entity is crucial, as its clinical overlap with other anterior knee pain causes can obscure diagnosis. The combination of radiography and MRI is essential to ensure accurate identification and appropriate management in the suspicion of patellar avulsion fractures in adolescents.