Synovial fluid is the thick liquid that lubricates your joints and keeps them moving smoothly . It’s on all of your joints, including in your knees, shoulders, hips, hands, and feet. Synovial Fluid Synovial fluid , present in very small quantities in normal synovial joints, has two functions: lubrication and nutrition.62,63 Synovial fluid is a combination of a filtrate of plasma that enters the joint space from the subsynovial capillaries and hyaluronic acid, which is secreted by the synoviocytes. A synovial fluid analysis is performed when pain, inflammation, or swelling occurs in a joint, or when there’s an accumulation of fluid with an unknown cause.