Tenosynovitis refers to chronic aseptic inflammatory changes in the tendon sheath caused by mechanical friction. Tenosynovitis is a common orthopedic disease, which is more common in manual laborers, especially those who repeatedly extend, flex, pinch and grasp with their fingers. It is more common in women than men. The tendon sheath is a kind of tendon auxiliary device. It is a double-layer sleeve-like structure surrounding the tendon formed by the connective tissue around the tendon to adapt to the sliding of the tendon. It is more common in the wrist, ankle, fingers, toes and other parts with long tendons and more activities. The tendon sheath is divided into two layers. The outer side is the fibrous tendon sheath, which is formed by the thickening of the transverse and oblique fibers of the deep fascia. It is attached to the bone and joint capsule, and plays the role of restraining, supporting, pulling and enhancing the tension of the tendon. The inner layer is the synovial tendon sheath, which is located in the fibrous tendon sheath. The synovial sheath is divided into two layers: visceral and parietal. The parietal layer is lined on the inner surface of the fibrous tendon sheath. The folded part formed on the bone surface is called the tendon entery, and the layer wrapped around the surface of the tendon is the visceral layer. The visceral and parietal synovium are closed at both ends to form a blind cavity, which contains a small amount of synovial fluid, which plays a role in lubrication and maintaining tendon mobility.