We report a case of an aneurysmal cyst localized in the patella of a 37-year-old man. The lesion was secondary to a chondroblastoma at six years follow-up after initial curettage and bone graft. It were no recurrence. Treatment of aneurysmal cysts depends on the degree of articular involvement. We made a detailed study of 11 cases of this rare localization of aneurysmal cysts reported in the literature.