Exceptional Massive Calcification of the Medial Collateral Ligament: A Case Linked to Underlying Lung Neoplasm.

Calcific tendinitis of the medial collateral ligament (MCL) is an exceedingly rare cause of knee pain. We report an exceptional case of massive, refractory MCL calcific tendinitis, with a unique presentation potentially linked to an underlying malignancy. A 61-year-old female patient presented with a 3-month history of persistent left medial knee pain, unresponsive to conservative therapy. Physical examination revealed medial joint line tenderness and limited range of motion. Imaging-including radiography, 3-dimensional computed tomography, and magnetic resonance imaging-demonstrated an unusually voluminous, strip-like calcific deposit within the proximal MCL. Notably, a concurrent lesion was identified in the left lung during the diagnostic workup and was subsequently confirmed as invasive lung adenocarcinoma. Given the failure of nonoperative measures and the large size of the calcification, open surgical excision was performed, leading to rapid and complete resolution of symptoms. This case highlights that massive, refractory calcific tendinitis may be a marker of systemic calcium dysregulation. The coexistence of invasive lung adenocarcinoma warrants consideration of an underlying systemic process, including potential metabolic dysregulation or paraneoplastic mechanisms that may contribute to periarticular calcification. We suggest that clinicians should evaluate for underlying metabolic and/or oncological disorders when atypical or massive periarticular calcifications are encountered. In such complex scenarios, open excision remains an effective definitive treatment if conservative measures fail.