Frequent sprains of the thumb root may be caused by a history of sprains, poor posture, and abnormalities of the musculo-neurological system. 1. History of sprains: It may be that after the thumb root joint has been sprained before, the internal repair of the joint has not been perfected, resulting in joint instability and asymmetric strength of muscles and tendons around the joint. When the patient is exercising or bearing weight, the thumb root will often be sprained. 2. Poor posture: incorrect posture during exercise can lead to joint injury and joint instability, which can also cause frequent sprains of the thumb root. 3. Tendonitis: it may be due to inflammation caused by striking, collision, etc., which can cause poor muscle strength, lower limb muscle incoordination and other phenomena, which can cause frequent sprains of the root of the thumb. It is recommended that patients with sprained thumbs go to the hospital in time and follow the doctor’s instructions for treatment to avoid delays.