Which component lubricates synovial joints?

• A. Synovial fluid
• B. Articular cartilage
• C. Bursae
• D. Ligaments

Answer: (A)

Lubrication of synovial joints is provided by synovial fluid, a viscous fluid secreted by the synovial membrane into the joint cavity. This fluid forms a protective film between the articulating surfaces of the bones, reducing friction and wear during movement, and it also helps nourish the avascular articular cartilage.

Articular cartilage itself provides a smooth, load-distributing surface but does not lubricate. Bursae are fluid-filled sacs that reduce friction where soft tissues rub against bones in other areas, not the joint cavity itself. Ligaments stabilize the joint and guide movement but do not serve as the lubricating component.