Knee edema usually refers to edema of the knee joint, and the causes include knee trauma, knee osteoarthritis, and chronic synovitis. 1. Knee trauma: Knee sprains, fractures, dislocations and other traumatic factors can cause knee edema, and imaging tests can reveal fractures, dislocations and intra-articular structural changes. 2. Knee arthritis: including gouty arthritis, rheumatoid arthritis, rheumatoid arthritis, chronic osteoarthritis of the knee, etc. The above mentioned diseases can cause obvious edema, inflammatory changes in the synovial membrane of the joints, and obvious pain can occur. 3. Chronic synovitis: the knee synovial cavity is the most extensive and complicated synovial cavity in the human joint. Because the knee joint is heavily loaded, fitness exercise, easy to suffer damage. Patients with chronic synovitis of the knee can have joint cavity effusion, edema and pain of the knee, and activity limitation. When there is edema of the knee, you should seek medical examination in time, early treatment after clear diagnosis, to avoid serious adverse consequences. Normally, joint protection should be strengthened to avoid trauma to the joints.