Under normal conditions, the intracellular and extracellular calcium ion concentrations are kept in dynamic balance. Modern medical research has found that when intracellular calcium ion concentration continues to increase, causing cellular excitation-contraction decoupling, it will lead to hypertension, myocardial infarction, heart failure, sudden death and other diseases, recently called intracellular “calcium deposition” or “calcium in-flow This is recently referred to as intracellular “calcium deposition” or “calcium endocytosis”. So, what tests are needed for calcium deposition due to calcium pyrophosphate? Here are the tests that need to be done for calcium deposition due to calcium pyrophosphate: 1. X-ray manifestations Calcium pyrophosphate deposition disease is mainly manifested on X-rays: calcification and arthropathy in 2 aspects. (1) Calcification: ① Cartilage calcium deposition most often involves fibrocartilage (such as the meniscus of the knee, the triangular bone of the wrist and the pubic symphysis), followed by hyaline cartilage (such as the hyaline cartilage of the knee, glenohumeral and hip joints), which appears on X-ray as a thick linear high-density shadow parallel to the subchondral bone, but not connected to the latter. Calcification of the joint capsule is less common than cartilage calcium deposits, mainly involving the metacarpophalangeal and knee joints, but severe calcification of the joint capsule can sometimes stimulate the development of osteochondroma. Calcification of the diffuse bursa is much rarer but is sometimes seen in the subacromial capsule, the eagle’s beak capsule, and the Achilles tendon capsule. They also appear as typical linear hyperintensities, unlike the isolated coin-like hyperintensities formed by hydroxyapatite deposits. Cartilage calcium deposits and soft tissue calcification are dynamic processes that can worsen as the disease progresses, but the lesion may appear less severe on X-ray during intervals when the thickness of the cartilage itself is reduced, during acute attacks, or when crystals are detached from the cartilage. It should be emphasized that the manifestation of calcification on X-rays is not an essential prerequisite for the diagnosis of calcium pyrophosphate deposition disease. (2) Arthropathy: The basic x-ray manifestations of pyrophosphate arthropathy are in fact the basic manifestations of osteoarthritis, including cartilage loss, cartilage sclerosis, cysts and bone redundancy formation, but the following two points can be distinguished from simple osteoarthritis: (1) the main joints and joints involved in pyrophosphate arthropathy are different from osteoarthritis, the lesions mainly involve the glenohumeral joint, metacarpophalangeal joint, ankle joint, elbow joint, radial (2) pyrophosphate arthropathy is characterized by the formation of a large number of bony redundancies and subchondral cysts on X-rays, commonly in the knee and wrist joints. When a patient’s arthrogram shows these typical signs, even if no signs of cartilage calcium deposition are found, pyrophosphate arthropathy may be considered. However, the coexistence of pyrophosphate arthropathy and osteoarthritis is often encountered in clinical practice, which requires a comprehensive judgment based on their respective predilection for different sites and typical manifestations. The results of a group of studies of pyrophosphate arthropathy X-rays monitored for 5 years have shown that the prognosis is relatively positive. The most common scenario is the development of bone remodeling and bony redundancy, while progressive bone and cartilage destruction is less common. The latter is most often seen in pseudoneuropathic arthritis and is often associated with severe wear of bone and cartilage and disintegrating fragments of bone. Although not a characteristic feature of pyrophosphatic arthropathy, the wear of the bony edges, especially the chronic wear of some of the smoother joints, is more widespread in actual cases, commonly in the front of the distal femur, the distal ulnar radius and the radial carpal joint. 2.Arthroscopic examination of gouty arthritis, showing most white-like crystals in the inner condyles of the femur. 3.Polarized light microscopy Monoclinic or triclinic (rectangular or rhombic) CPPS crystals with faint positive bifractionation seen under polarized light microscopy. 4.Pathological examination Unlike sodium urate crystals, calcium pyrophosphate crystals are not deposited in all connective tissues, but tend to be limited to various structures of the motor system. Numerous pathologic findings show that crystals are usually deposited first in cartilage and, in rare cases, in joint capsules and tendons, while crystal deposition in synovial bursae or tendon sheaths is secondary to the former. Calcium pyrophosphate crystals are most often deposited in the middle zone of cartilage, with small bead-like “stones” in the middle of the specimen. Microscopically, small, well-defined, mostly rounded deposits are often adjacent to hypertrophic cartilage lacunae in the early stages, but as the crystals develop, the cartilage surface is often involved. The cartilage around the crystal deposits often loses its heterogeneity, and protofibrous degeneration is seen, accompanied by chondrocyte metaplasia and proliferation, and the accumulation of lipid droplets and proteoglycans in the hypertrophic chondrocytes. Partial or total cartilage destruction is seen in severe cases. In the subchondral bone, thickened trabeculae and numerous small cysts may be seen, and sometimes the rupture and fusion of small cysts may lead to fracture. In the synovium, calcium pyrophosphate crystals are usually deposited in the interstitial spaces and synovial cells on the synovial surface, and the deposition sites are often surrounded by fibroblasts and connective tissue. The acute phase is characterized by proliferation of synovial cells with a large infiltration of neutrophils and lymphocytes, whereas the chronic phase is typically characterized by a significant infiltration of fibrotic mononuclear cells and the formation of giant cell granulomas around the crystals. The pathological changes of calcium pyrophosphate deposits in the joint capsule and tendon sheath are similar to those of synovium. If a large number of weakly positive birefringent light rod-shaped crystals with a diameter of about 2-10 μm can be seen in the cells under phase contrast polarized light microscopy, combined with the clinical symptoms and features of cartilage calcium deposition, joint capsule calcification or bone redundancy formation on X-ray, the diagnosis of this disease can basically be made, but also However, culture and smear of joint fluid must be performed to exclude the diagnosis of septic arthritis. It is sometimes difficult to distinguish the disease from osteoarthritis based on X-ray alone, and joint pathology biopsy is rarely used in the diagnosis of this disease because it is difficult to be accepted by patients.