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, which does not have its own blood supply. In addition to lubrication, synovial fluid acts as a shock absorber, helping to distribute pressure evenly across the joint. It contains hyaluronic acid and lubricin, which contribute to its viscous nature. Overall, synovial fluid plays a crucial role in maintaining joint health and function.