The tendon sheath is a bursa that protects the tendon and has two layers, an inner and an outer layer with synovial fluid between them, which reduces friction during tendon movement. The tendon sheaths are found in the wrist, metacarpals, feet and shoulder biceps tendon grooves. It protects the tendons from friction and compression by bones and other tissues and ensures that the tendons are lubricated and have adequate mobility. Tenosynovitis can occur in the fingers, toes, wrists, ankles and shoulders, with the wrists and fingers in particular being the most common. For example, radial styloid sheathing and finger tenosynovitis. Tendonitis is mainly caused by high activity or excessive force or chronic cold irritation of the tendon in a short period of time, and it is more common in women.