Imaging features of crystal-induced arthropathy.

Crystal-induced arthropathies constitute a spectrum of inflammatory arthritides that is induced by cellular reaction to crystal deposition in and around joints. A variety of microcrystals may be deposited and can induce an inflammatory response. The three most common types of crystal-induced arthropathy are gout, calcium pyrophosphate dihydrate deposition disease, and calcium hydroxyapatite deposition disease. Each has a characteristic clinical presentation, crystal type that may be aspirated from affected tissues, and radiographic appearance. Each of these entities may occur as a primary abnormality or secondary to an underlying disorder. Sometimes these diseases may coexist in the same joint or individual. Imaging frequently plays a crucial role in the diagnosis of crystal-induced arthropathies and may help to monitor disease progression and treatment response.