The synovial membrane of a synovial joint produces and maintains proper levels of synovial fluid. As explained by Johns Hopkins, the synovial membrane is tissue that lines the joint and seals it into a joint capsule. Synovial fluid is a clear, viscous liquid that fills the joint capsule for lubrication.
Inside the joint capsule, layers of articular cartilage provide padding for the articulating bones. The articular cartilage soaks up synovial fluid like a sponge, explains Dr. Joseph M. Mansour. The fluid in articular cartilage effectively acts as a reserve of synovial fluid. During movement, synovial fluid is squeezed out mechanically, maintaining a level of fluid in the joint cavity and on the cartilage surface.