Avulsion Fracture at the Femoral Origin of the Medial Head of the Gastrocnemius in an Adolescent: A Case Report with Two-Year Clinical Follow-Up.

Avulsion fractures at the femoral origin of the medial head of the gastrocnemius are exceptionally rare, particularly in skeletally immature patients, and may be overlooked when evaluating acute posterior knee pain. A previously healthy 13-year-old boy developed acute posteromedial left knee pain and felt a sudden pop while running. He could bear weight with difficulty and held the knee in slight flexion because terminal extension was painful. Examination showed focal posteromedial tenderness, preserved motion with pain at full extension, and an intact distal neurovascular status. Plain radiographs demonstrated a small osseous fragment posterior to the distal femur. Magnetic resonance imaging (MRI) identified a 1.2 × 0.5 cm minimally displaced, partially corticated fragment arising from the femoral origin of the medial head of the gastrocnemius, with no associated ligamentous, meniscal, or musculotendinous injury. The patient was managed with a long-leg cast at 30° of knee flexion for six weeks, followed by six weeks of supervised range-of-motion, stretching, and strengthening exercises. He regained painless full range of motion, normal strength on clinical examination, and a stable knee, and subsequently returned to sports without reported pain or functional limitation. At two-year clinical follow-up, he remained asymptomatic without instability or treatment-related complications. This case adds to the limited pediatric literature on this uncommon injury and highlights the role of MRI in characterizing the lesion and excluding associated injuries. Because no follow-up imaging was obtained, the outcome represents clinical recovery rather than radiographically confirmed osseous union.