Chondroblastoma of the patella presenting as knee pain in an adolescent.

We report a case of chondroblastoma of the patella, associated with an aneurysmal bone cyst and pathologic fracture, that presented as knee pain in a 13-year-old girl. This case is the fifth case in the literature that associates patellar chondroblastoma with fracture, which should probably be regarded as a significant feature of this lesion.