The<unk>  is defined by presence of joint inflammation and the presence of CPPD crystals within the joint. The crystals are usually detected by imaging and/or joint fluid analysis. X-ray of a knee with chondrocalcinosis. Medical imaging, consisting of x-ray, CT, MRI, or ultrasound may detect chondrocalcinosis within the affected joint, indicating a substantial amount of<unk>  crystal<unk>  within the cartilage or ligaments. Ultrasound is a reliable method to diagnose CPPD. Using ultrasound, chondrocalcinosis may be depicted as echogenic foci with no acoustic shadow within the hyaline cartilage or fibrocartilage. By x-ray, CPPD can appear similar to other<unk> s such as ankylosing spondylitis and gout. Micrograph showing crystal<unk>  in an intervertebral disc. H&E stain. condenser. Arthrocentesis, or removing synovial fluid from the affected joint, is performed to test the synovial fluid for the<unk><unk>  crystals that are present in CPPD. When stained with H&E stain,<unk><unk>  crystals appears deeply blue ("basophilic"). However, CPP crystals are much better known for their rhomboid shape and weak positive birefringence on polarized light microscopy, and this method remains the most reliable method of identifying the crystals under the microscope. However, even this method suffers from poor sensitivity, specificity, and inter-operator agreement. These two modalities currently define CPPD<unk> , but lack diagnostic accuracy. Thus, the diagnosis of CPPD<unk>  is potentially epiphenomenological.
Calcium pyrophosphate dihydrate crystal deposition disease
Gout
Ectopic calcification
Metastatic calcification
AA amyloidosis
Secondary systemic amyloidosis
Crystal arthropathy
Cartilage tumor