Pellegrini-Stieda Disease

Pellegrini-Stieda lesions refer to heterotopic ossification involving the medial collateral ligament (MCL), typically located at or near its proximal insertion on the medial femoral condyle. These lesions are most often identified radiographically as elongated or curvilinear calcifications that develop following trauma, chronic traction, or repetitive stress to the MCL origin. The lesions are named after early 20th-century surgeons Augusto Pellegrini and Alfred Stieda. However, the first radiologic description of this process was documented by Köhler in 1903, predating the more widely recognized publications of Pellegrini (1905) and Stieda (1908). The term "Pellegrini-Stieda lesion" specifically denotes the radiographic finding of ossification at the MCL origin. In contrast, Pellegrini-Stieda disease (or syndrome) refers to the clinical condition characterized by such ossification in conjunction with medial knee pain, stiffness, or restricted range of motion (ROM). While many lesions are asymptomatic and incidentally discovered on imaging, symptomatic cases are usually associated with prior MCL injury, particularly grade II or III sprains, and may present weeks to months after the initial trauma. Adjacent structures may also be affected, with calcific deposits reported in the distal adductor magnus tendon. Distinguishing between a radiographic lesion and the symptomatic disease is clinically important. Conservative treatment, including rest, physical therapy, and nonsteroidal anti-inflammatory drugs (NSAIDs), is effective in most cases, though surgical excision may be required for persistent or functionally limiting symptoms.