The causes of pain when clenching a fist include muscle strain, tenosynovitis, nerve injury and so on. 1. Muscle strain: due to strenuous exercise, high-intensity labor, etc., the patient’s hand is overworked, resulting in muscle strain in the hand, which triggers the patient’s hand to have pain when he or she clenches his or her fist. 2. Tenosynovitis: If patients use their hands for a long time to work, such as playing the keyboard and mouse, playing a musical instrument, etc., resulting in chronic aseptic inflammation of the hand, the formation of tenosynovitis, the constant stimulation of inflammatory factors, resulting in the patient’s fist when clenched, you will feel pain. 3. Nerve injury: due to trauma, surgical injury, etc., caused by the median nerve, ulnar nerve, radial nerve and other injuries to the patient’s hand, when the patient to make a fist movement, will cause the nerve to be pulled, triggering pain in the patient’s hand symptoms. If the patient appears to tighten the fist on the pain of the situation, it is recommended that the patient go to the hospital in time to improve the relevant examination, to clarify the cause of the disease, and follow the doctor’s instructions for treatment.