The etiology of tendon sheath cysts is currently unknown, and may be caused by exertion, trauma to the tendon, etc. 1. Exertion: tenosynovial cysts are common in patients who have been repeatedly working with their hands or wrists for a long time, and it is common to see cystic swelling in the tendon sheaths of the wrists and fingers. This is due to the repeated friction of the tendons caused by the long-term repeated working with the fingers and wrists, which results in localized injuries and leads to the formation of tenosynovial cysts. 2. Trauma to the tendon: When there is a history of trauma to the tendon, cystic swelling can also appear in the tendon sheath, which can be multiple or single. Patients with tendon sheath cysts usually have no obvious symptoms, and if necessary, consult a doctor in time, and do not squeeze or pinprick on your own.