This chapter discusses crystal synovitis. Crystal synovitis results from deposition of various types of crystals in and around joints. Commonly deposited crystals are monosodium urate monohydrate crystals (in gout), calcium pyrophosphate dihydrate (CPPD) and hydroxyapatite (HA) deposition. Crystal synovitis is seen mainly in three conditions: (1) gout, (2) pseudogout, and (3) CPPD disorders. This chapter also discusses the diagnosis and treatment of crystal synovitis. Pseudogout requires symptomatic treatment in the form of anti-inflammatory drugs and analgesics.