The right index finger can be extended but not bent, considering tendon injury, tenosynovitis, arthritis, infection and other causes.
1. Tendon injury: Traumatic injury causing rupture of the superficial or deep flexor tendon of the index finger, and the presence of the extensor tendon can lead to the inability of the index finger to bend, but the extension of the index finger is normal.
2. Tenosynovitis: Mechanical friction can lead to aseptic inflammation of the tendon sheath surrounding the flexor tendon, resulting in edema and fibrous degeneration, and the tendon is blocked from moving within the tendon sheath, resulting in inability to flex the finger.
3. Arthritis: degeneration of the metacarpophalangeal joint or interphalangeal joint of the index finger, or fracture caused by joint surface damage, etc., can lead to arthritis, resulting in swelling of the finger joints and inability to bend.
4. Infection: Bacterial invasion can lead to purulent dactylitis, swelling, pain, accompanied by the inability to bend the finger.
There may be other reasons why the right index finger cannot be bent, so it is recommended that you go to a regular hospital and be treated under the guidance of a physician.