[Ectopic calcification of the knee joint].

An 81-year-old man presented with progressive tumorous swelling of the infrapatellar region of the left knee joint. X‑ray imaging was suggestive of bursosynovial chondromatosis or ectopic calcification. Histopathological examination of the resected tissue combined with laboratory findings of renal insufficiency and secondary hyperparathyroidism led to the diagnosis of tumoral calcinosis, which is a rare subentity of ectopic calcification.