[Role of radiology in the diagnosis of joint chondrocalcinosis. Calcium pseudogout]

Chondrocalcinosis is a really frequent clinicopathologic entity, which is caused by the penetration of calcium pyrophosphate dihydrate microcrystals into the structures of the joint, including hyaline cartilages and fibrocartilages--hense its name--as well as the synovial fluid and membrane. Calcium gout, which preferentially appears in the knees, is the most spectacular and characteristic symptom of chondrocalcinosis, expressing a crisis of acute microcrystal synovitis, of which it has all the usual clinical features, and thus simulating uratic gout. The positive diagnosis is based on: a) the radiologic demonstration of articular calcifications in the lining cartilages, forming a continuous or fragmented opaque border on the subchondral bone, from which it is separated by a light space, and/or in the fibrocartilaginous structures (most often the menisci, the symphysis pubis, the disk of the inferior radioulnar joint) where they appear as small, irregular clusters with blurred or cloudy margins. The knee is the most frequent site of calcium impregnation images, both in hyaline cartilages and in fibrocartilages. b) the presence of calcium pyrophosphate microcrystals in the synovial fluid; their nature is usually demonstrated convincingly enough with a conventional light microscope; c) needle biopsy findings of microcrystalline clusters embedded in the synovial membrane, that can be easily identified with routine staining. In practice, demonstrating radiologic signs, when these are characteristic and can be detected in their preferred sites, allows recognizing diffuse chondrocalcinosis in satisfactory safety conditions after a calcium gout crisis, as well as in the presence of the many atypical or misleading symptomatic aspects of this microcystal arthropathy, that will be the subject of a further paper.