Pseudogout associated with meniscal cysts - report of two patients.

Two patients with pseudogout developed large meniscal cysts at the knee. In the first case the diagnosis of meniscal cyst was confirmed surically. In the second case, the cyst resolved following thorough aspiration. Polarized microscopy of repeated aspirated from cyst in this case as well as of fluids from the knees of both patients consistently showed positively birefringent rhomboid crystals. X-ray diffraction of fluids from the knee of the second patient identified the crystals as calcium pyrophosphate dihydrate.