The inability to flex and extend the fingers may be caused by tenosynovitis. Tenosynovitis refers to a chronic, sterile inflammatory change in the tendon sheath caused by mechanical friction. In daily life and work, frequent activities cause excessive friction, and this mechanical stimulation can cause the tendon sheath to become congested, edematous and other sterile inflammatory reactions. Repeated trauma or prolonged changes such as chronic fibrous connective tissue hyperplasia, hypertrophy, and adhesions occur. The thickness of the tendon sheath may increase from positive to 2~3 times normal, and the thickening of the tendon sheath may lead to narrowing of the tendon sheath, adhesions between the tendon sheath and the tendon may occur to different degrees, and the tendon may become degenerative and deformed, presenting a gourd shape with thickened ends or a fusiform shape with enlarged middle and thin ends at the damaged area, which may cause local pain and pressure or limited joint movement. Early or mild cases can be treated with non-surgical methods, including reduction of hand activity, physical therapy and intra-tendon sheath injections. If non-surgical treatment does not work or if there are repeated episodes of tendon sheath stenosis, a small needle or surgery can be used to release the stenotic tendon sheath.