Synovitis of the knee is an inflammation of the synovial membrane that surrounds the knee, according to the Virtual Sports Injury Clinic. The synovial membrane keeps the knee lubricated.
The symptoms of knee synovitis include stiffness, pain and swelling in the joint, explains the Virtual Sports Injury Clinic. The knee is also red and feels hot. A diagnosis of synovitis is made when fluid is aspirated from the knee and sent to a lab to be tested.
Knee synovitis can be a sports injury, but it is also a complication of gout or rheumatoid arthritis, says the Virtual Sports Injury Clinic. It may even appear for no known reason.