Diagnosis of calcium pyrophosphate deposition
A definitive diagnosis of calcium pyrophosphate deposition is made by identifying calcium pyrophosphate dihydrate crystals in synovial fluid (see Utility of joint aspiration and synovial fluid analysis for rheumatological diseases). The synovial fluid may contain both monosodium urate and calcium pyrophosphate dihydrate crystals—if identified, seek specialist advice. Microscopy and culture of the synovial fluid should also be undertaken to exclude septic arthritis.
While the presence of chondrocalcinosis on X-ray supports the diagnosis of calcium pyrophosphate deposition, it is neither highly sensitive nor specific. Furthermore, the finding of chondrocalcinosis on X-ray does not necessarily indicate the presence of clinical disease; it may be asymptomatic without need of management. The incidence of chondrocalcinosis increases with age: from 65 to 74 years the incidence is 15%, from 75 to 84 years it is 36%, and after the age of 84 years it is almost 50%. Chondrocalcinosis most commonly affects fibrocartilage (particularly the knee and triangular cartilage of the wrist). It may also occur in hyaline cartilage (mainly knee and glenohumeral joints) as linear opacities separate from, and often parallel to, subchondral bone. The location of the chondrocalcinosis is important for determining its relevance to clinical disease. For example, chondrocalcinosis involving the triangular cartilage of the wrist is much more likely to be associated with clinical disease than chondrocalcinosis involving the kneeGamon, 2015.