Patients with rheumatoid arthritis wake up in the morning with stiff hands and difficulty in making fists, which improves only after activity. Morning stiffness is a very prominent clinical manifestation of rheumatoid arthritis. The duration of morning stiffness should be calculated from the time the patient starts to move after waking up until the time when the patient’s morning stiffness is significantly reduced, usually measured in minutes. The cause of morning stiffness is the accumulation of edema fluid in the inflammatory tissues during sleep or reduced exercise, which causes swelling of the tissues around the joints. After the patient moves, as the muscles contract, the edema fluid is absorbed by the lymphatics and small veins and the morning stiffness is relieved. Therefore, joint stiffness can also occur during the day, and is in fact the same thing as morning stiffness, as long as the affected joint activity is reduced or maintained in the same position for a longer period of time. Patients with rheumatoid arthritis have morning stiffness in the acute or active phase of the disease, and the duration is directly proportional to the severity of the synovitis. Patients with ankylosing spondylitis, osteoarthritis, and systemic lupus erythematosus can all have morning stiffness, but it rarely lasts more than an hour as in rheumatoid arthritis. Patients with rheumatoid arthritis should indicate whether they have morning stiffness and how long it lasts when they visit the doctor, as this can be helpful in diagnosing the condition. As rheumatoid arthritis goes into remission, the duration of morning stiffness shortens and its degree decreases, so morning stiffness is a good indicator of the severity of systemic inflammation.