The causes of hand joint deformation include local trauma, overuse of the hand or autoimmune diseases. 1. Local trauma: local trauma may be caused in the process of strenuous hand activities or heavy physical labor. For example, there are fractures, dislocations and other injuries to the hand. This may result in localized joint deformities. 2. Excessive use of the hand: Prolonged use of the hand for heavy physical labor, such as lifting heavy objects or holding agricultural tools for labor. This will cause overuse of the small joints of the hands, which may cause osteoarthritis in the above areas over time, and then cause deformities in the relevant areas. 3. Autoimmune lesions: due to genetic factors, or upper respiratory tract infections, which induces an abnormal immune response in the body. Thereafter, the small joints in the hand, especially the synovium, ligaments and other structures inside the joints, will be attacked by the autoimmune system. This results in deformities of the hand, and in the case of severe lesions, deformities such as pointer fingers, button fingers, swan necks, etc., may even occur. It is recommended to go to the hospital promptly after the appearance of these conditions.