Chondrocalcinosis in an isolated suprapatellar pouch with recurrent effusion.

We report the case of a 45-year-old man with a long history of chondrocalcinosis and recurrent painless suprapatellar swelling. Over the 3 months before his admission, the swelling had become persistent and extended 10 cm proximal to the patella on the anterior aspect of the thigh. Magnetic resonance imaging revealed an enlarged suprapatellar pouch that was completely separated from the knee joint cavity by a suprapatellar membrane. Arthroscopic treatment consisted of complete removal of the membrane, creating a passage to the articular cavity, and debridement of the synovial calcifications. The patient was followed-up postoperatively for 2 years and no recurrence of the swelling was reported during this period of time. Two potential mechanisms might have been responsible for the persistent swelling: (1) chondrocalcinosis led to effusion of a suprapatellar pouch that was originally isolated from the knee joint cavity, or (2) the suprapatellar pouch was separated from the knee joint cavity as a result of an incomplete involuted suprapatellar plica that became adherent during recurrent inflammation due to chondrocalcinosis.