Which fluid is found within a synovial joint?

• A. Blood.
• B. Lymph.
• C. Synovial fluid.
• D. Mucus.

Answer: (C)

Synovial joints contain a specialized lubricating fluid in the joint cavity called synovial fluid. This fluid is produced by the synovial membrane lining the joint capsule and serves to reduce friction between the moving ends of bones (articular cartilage), cushion the joint, and nourish the avascular cartilage. It’s typically viscous and contains hyaluronic acid, giving it its slippery quality.

Blood, by contrast, flows through blood vessels; it isn’t stored in the joint space. Lymph travels through the lymphatic system, not the joint cavity. Mucus is produced by mucous membranes and lines passages like the respiratory and digestive tracts, not joints. Therefore, the fluid found within a synovial joint is synovial fluid.