Possible causes of ring finger inability to bend include tenosynovitis, joint destruction, and nerve damage to the finger. 1. Tenosynovitis: In tenosynovitis, the tendon becomes edematous and thickened within the tendon sheath, which may cause symptoms of entrapment, resulting in the inability to bend and straighten the finger normally. 2. Joint destruction: Diseases such as arthritis, rheumatoid arthritis, gouty arthritis, etc. may lead to joint destruction, which may result in joint stiffness and inability to bend the fingers. 3. Damage to the nerves of the fingers: When the nerves that innervate the movement of the ring finger are damaged, it will also lead to the inability to bend the finger. When the symptoms of the ring finger can not be bent, if after resting and braking, hot compresses and other simple treatment, but still can not be relieved, it is recommended to consult a doctor in a timely manner, to clarify the cause of the disease for targeted treatment.