Synovial osteochondromatosis and pseudogout

A middle aged male developed recurrent episodic inflammatory effusions of the right knee associated with radiographic findings consistent with osteochondromatosis. Calcium pyrophosphate dihydrate (CPPD) crystals were identified by polarized light and electron microscopy, although chondrocalcinosis was not demonstrated radiographically in this joint or any other locations. Analysis of noninflammatory fluid from the left knee demonstrated apatite crystals. The unique association of CPPD crystals and synovial osteochondromatosis without evidence of chondrocalcinosis and the relationship of these 2 entities is discussed.