The most important symptom of osteoarthritis of the knee is pain. Pain can be distinguished from location, and familiarity with anatomy can help determine the damage to different structures of the joint; while another way of classification – from pain mechanism is more difficult, if it can be analyzed from symptoms, signs, experience, images, occupation, triggers and many other aspects The cause of current pain, and targeted selection of different drugs, physical modalities, surgical modalities, and effective relief of pain in the short term and be corroborated. A common clinical example is that several patients with knee pain are given anti-inflammatory and pain-relieving drugs, but some of them work and others not so much, because the mechanism must be different and one drug cannot solve it. Combining the information, the following different mechanisms of osteoarthritis pain were summarized. 1. Pain due to muscle strain and fatigue caused by overuse. Commonly caused by quadriceps or N cord muscle pain after over-exercise or climbing by people who do not exercise for years. Rest, topical medicine and physical therapy are effective. 2.Bone contusion caused by microfracture of subchondral trabeculae. It is common in the elderly who think they can ignore the trauma, often mistaken for an acute attack of osteoarthritis (the next condition), with severe pain, clinical symptoms similar to a fracture, no change on X-ray, and MRI can reveal edema and contusion in the bone marrow. This type of pain lasts for a long time, requires sedation, and central analgesic drugs are more effective. 3. Irritation of the subperiosteal nerve – stimulation by inflammatory substances. The most common clinically, the pain is triggered by inflammatory substance stimulation after cold and exertion. Such pain is most effectively caused by non-steroidal anti-inflammatory drugs, such as fenbuterol and fotarol. 4. Irritation of ligaments and stops of the joint capsule – from deformity of the bone, poor force lines of the lower extremity or irritation from severe swelling and exudation of the joint. Local treatment of such pain – closure or small acupuncture therapy of Chinese medicine is effective. 5. Venous congestion during the remodeling phase of the subchondral bone. This type of pain is not severe, periodic, mostly pain at night, pain at rest, and more common in the upper calf. General pain medication is ineffective, and the use of blood-activating drugs and drugs to improve microcirculation may be effective. 6. Pain only when walking up and down stairs or squatting – pain caused by increased pressure in the patellofemoral joint. Quadriceps exercise, weight control, and cartilage nutrition drugs seem to be more effective. 7.Pain caused by the wear and tear of meniscus in the elderly. An inadvertent sprain or a meniscus rupture caused by prolonged squatting. Need to rest and rest for a long time, if necessary, if the physical condition can not be surgically treated, intra-articular closure can quickly relieve pain.