Synovial fluid is a thick, clear liquid found in the cavities of synovial joints, such as the knees and elbows. Its primary function is to lubricate the joints, reducing friction between the cartilage surfaces during movement. This fluid also provides essential nutrients to the cartilage, helping to maintain its health and function. In addition to lubrication, synovial fluid acts as a shock absorber, cushioning the joints during physical activities. It is produced by the synovial membrane, which lines the joint capsule. Proper levels of synovial fluid are crucial for joint mobility and overall joint health.