If you can’t stretch your hand straight and feel your tendons are constricted, it is related to physiological factors, tenosynovitis, rheumatoid arthritis and so on. 1. Physiological factors: If you are engaged in high-intensity physical activities that require frequent exertion of the hand, it can cause muscle strain of the hand, which is manifested by the inability to straighten the hand and the feeling that the tendon is shrunken, or it may be that you have been shrinking your hand, which leads to shortening of the tendon and difficulty in straightening it out. Generally through a period of rest will return to normal. 2. Tendovaginitis: patients with this disease may also have different degrees of redness, swelling, pain and other symptoms. At the onset of the disease, the symptoms can be improved through physical therapy, such as localized hot compresses and so on. If the disease is serious, tenosynovectomy is needed to release the surgery. 3. Rheumatoid arthritis: this disease will have obvious morning stiffness, accompanied by swelling, pain, etc., can show the hand can not be straightened, feel the tendon is shrinking symptoms. After a clear diagnosis, glucocorticoids and drugs to improve rheumatism can be used. If the symptom of not being able to straighten the hand and feeling that the tendons are constricted persists, it may be ischemic contracture, and it is recommended to go to the hospital in time, and treat the cause of the disease.