Causes of knee swelling and pain include synovitis and knee trauma, as follows: First, synovitis: In synovitis secondary to degenerative osteoarthritis of the knee, patients will have joint effusion, knee swelling, as well as knee pain and limited movement. The patient’s symptoms are more pronounced when walking under weight, and MRI will reveal joint effusion and inflammatory synovial hyperplasia. Second, knee trauma: such as joint fractures, ligament tears, meniscal injuries, and articular cartilage injuries can cause knee swelling, pain, and limited movement. MRI examinations can reveal the location and severity of the lesion. After swelling and pain in the knee joint, the appropriate treatment should be chosen according to the cause, such as cold braking for trauma, or braking and resting physical therapy for chronic inflammation. After treatment, knee swelling and pain will gradually ease or even disappear completely.