Tendovaginitis: A disease caused by hypertrophy and narrowing of the sheath tube due to repeated friction. Repeated stretching, flexing, gripping and pinching are prone to this disease. It is more common in men. (Recently, however, all the patients are women, so don’t be surprised if they see it). It occurs in the tendon sheath of the flexor muscle of the finger, also known as trigger finger (common in the thumb), with pressure and pain on the palmar side of the metacarpophalangeal joints and popping sound when flexing and extending the fingers. Kelvin’s disease occurs in the radial tuberosity and is a tendinitis of the short extensor tendon and the extensor hallucis longus tendon. It is characterized by localized tenderness and pain when the thumb is held with all four fingers and ulnarly deviated from the wrist. Collagen disease is also associated with this condition. In young children, first-degree stenosis of the sheath is occasionally seen in the tendon of the flexor digitorum longus. Rest or localized corticosteroid closure is effective. If this is not effective, tenotomy is performed. To put it plainly: tendons are what we often call sinews, which drive the joints to move. But there are so many tendons in the human body, there is no rule how to do, then we need the tendon sheath to give it constraints, like a spell to fix it in the corresponding position, the tendon can only be within its range of activities. The tendon can only move within its range of motion. The tendon is more active, thicker, and stiffer. The tendon sheath is overburdened, but is tough and refuses to compromise. When the two fight, tenosynovitis occurs, and ultimately there is an obstacle to movement. There is no way to make the tendon slimmer, but we have to give in to the tendon sheath, throw in the towel, and let the tendon return to freedom, and society will be in harmony.