Knee pain in the morning can be caused by the following reasons: First, osteoarthritis of the knee, patients with osteoarthritis of the knee can have symptoms of knee pain after waking up in the morning, which can be accompanied by morning stiffness, accompanied by limited knee movement, which should be checked early, early examination of the knee X-ray, CT and MRI for early diagnosis and early treatment. Second, rheumatoid, when rheumatoid involvement of the knee joint can have the symptoms of morning stiffness, and can be accompanied by morning knee pain, knee pain can be improved after a short period of activity, then we should check blood tests and take x-ray, CT of the knee joint to diagnose. Third, ankylosing spondylitis, severe ankylosing spondylitis can involve the knee joint, resulting in morning knee pain and stiffness, which can be accompanied by pain in the sacroiliac joint, which should be diagnosed by blood tests and x-ray of the knee joint, as well as x-ray of the sacroiliac joint and lumbar spine.