The cause of tenosynovitis is the repeated mechanical friction between the local tendon and tendon sheath, leading to chronic aseptic inflammatory changes. It is often related to repeated activity in the affected area. Excessive repetitive movement of the affected area causes local congestion, exudation, edema, and other inflammatory changes. The stimulation of inflammatory factors leads to local pain and discomfort. As the condition progresses, thickening of the tendon sheath causes the local tendon to move less smoothly within the sheath, thereby causing restricted local movement. Additionally, tenosynovitis in infants and young children is often considered to be caused by congenital factors.