Radiographically dense calcium pyrophosphate dihydrate (CPPD) crystals are deposited in cailage and joint soft tissues in pseudogout, which can involve the knees, wrists, elbows, shoulders, or ankles. If the patient is asymptomatic because the deposition is primarily within cailage, the condition is sometimes called chondrocalcinosis. In its more severe form, the joint involvement can clinically resemble rheumatoid ahritis. Neither gonococcal ahritis, osteoahritis, nor rheumatoid ahritis are associated with crystal formation. The monosodium urate crystals deposited in joints in gouty ahritis are not radio-opaque. Ref: Wyatt C., Kemp W.L., Moos P.J., Burns D.K., Brown T.G. (2008). Chapter 19. Pathology of the Bones and Joints. In C. Wyatt, W.L. Kemp, P.J. Moos, D.K. Burns, T.G. Brown (Eds), Pathology: The Big Picture.