The tenosynovial sheath is a double-layered cannula-like closed synovial tube outside the tendon, which is the synovial sheath that protects the tendon. It wraps around the tendon in two layers, with a cavity between the two layers, the synovial cavity, containing the synovial fluid of the tendon sheath. The inner layer is closely attached to the tendon, and the outer layer is lined inside the tendon fiber sheath, which together with the bone surface, has the function of fixing, protecting and lubricating the tendon from friction or compression. If the tendon is rubbed excessively for a long period of time, an inflammatory injury to the tendon and tendon sheath can occur, causing swelling, called tenosynovitis. If left untreated, it may develop into permanent mobility problems. The symptoms of tenosynovitis: 1, radial stenosis tendinitis The performance is characterized by pain on the radial side of the wrist joint and is closely related to the thumb activity. The disease occurs mostly in women over 40 years of age, but it also develops in lactating women. 2, flexor tendon stenosis tenosynovitis often occurs in the thumb, middle, ring finger, the age of onset is generally above 40 years. The initial onset of the disease produces popping and pain during finger flexion and extension, so it is also called “trigger finger”. Patients often report joint immobility and joint swelling. In severe cases, the joint is locked in the flexion or extension position, and the joint cannot be straightened or flexed. The disease is occasionally seen in pediatric patients with bilateral thumbs in the flexed position and unable to actively straighten. In mild cases, the thumbs can be straightened by local massage when the child is asleep, but in severe cases, the thumbs cannot be straightened even passively. 3, myosynovitis Myosynovitis is also known as gravel myosynovitis. When the wrist activity increases, the proximal side of the dorsal wrist appears red, swollen, feverish, local pressure pain, pressure can produce twisting sounds or tread snow sound. 4, ulnar carpal extensor tendinitis is one of the causes of ulnar pain of the wrist joint. The tendon of the ulnar carpal extensor and the surrounding sheath play an important role in supporting the distal radial-ulnar joint and the carpal triangle fibrocartilage complex. During excessive wrist activity, repeated strains or sprains can trigger ulnar carpal pain, especially when the wrist is sore and weak during exertion.