Calcificación del ligamento colateral medial de la rodilla: una causa rara de dolor en la rodilla que simula un síndrome de Pellegrini-Stieda

Symptomatic soft tissue calcifications in the knee are rare in comparison with calcific tendinitis of the rotator cuff and can cause severe pain mimicking internal derangement. We present the case of a 45-year-old woman with pain and swelling at the medial side of the knee with no antecedents of trauma. Radiographs showed calcified deposits within the medial collateral ligament. Magnetic resonance imaging confirmed the diagnosis of calcific tendinitis demonstrating its location within the ligament with adjacent soft-tissue reaction. This diagnosis can be initially mistaken for Pellegrini-Stieda disease. Exclusion of an antecedent of trauma, calcific characteristics of the deposits and detection of inflammatory changes in the soft tissue around the ligament allow diagnosis without the need for histological confirmation of crystal deposition. The patient underwent conservative treatment with complete symptom resolution.