The causes of inflexible bending and straightening of the ring finger may include tenosynovitis, joint inflammation, and nerve damage of the finger. 1. Tenosynovitis: In tenosynovitis, due to edema and thickening of the tendon, the tendon may be stuck in the tendon sheath, resulting in inflexible bending and straightening of the ring finger. 2. Joint inflammation: diseases such as osteoarthritis, rheumatoid arthritis, gouty arthritis, etc. can lead to destruction of cartilage in the finger joints, resulting in stiffness and inflexibility in bending and straightening. 3. Damage to finger nerves: When the nerves innervating the extension and flexion activities of the ring finger, such as the ulnar nerve, are damaged, it can also lead to symptoms such as bending, straightening inflexibility or even inability to move. Diseases that cause inflexible bending and straightening of the ring finger also include intra-articular free body and fracture, etc. It is recommended to consult a doctor in time and receive appropriate treatment after clarifying the cause of the disease, which should not be taken lightly in order to avoid delaying the condition.