Inflexibility and weakness of the left hand may be caused by chronic strain and trauma, or it may be caused by cervical spondylosis and other diseases. 1. Chronic strain: If the left hand is chronically strained for a long time, too much activity may make the muscles of the left arm contract weakly, resulting in weakness and inflexibility of the left hand. 2. Trauma: If there is a history of trauma to the left hand, it may lead to nerve damage in the left hand, causing symptoms of weakness and inflexibility in the left hand. 3. Disease: If the patient has spinal cord cervical spondylosis, cerebral infarction and other diseases, the nerves may be compressed, resulting in abnormal central nervous system function, leading to inflexibility and weakness of the left hand, accompanied by pain and numbness of the left upper limb. Patients with symptoms of left hand inflexibility and weakness are advised to go to the hospital for examination and treatment as soon as possible.