Which term denotes the fluid that lubricates joints?

• A. Hyaline
• B. Fibrous
• C. Tendinous
• D. Synovial

Answer: (D)

The fluid that lubricates joints is synovial fluid. In a synovial joint, the inner lining (the synovial membrane) produces this viscous fluid that fills the joint cavity. It reduces friction between the smooth surfaces of the articulating bones, cushions them during movement, and helps deliver nutrients to the avascular cartilage. The term synovial relates to this membrane and its fluid, the substance that lubricates the joint. The other terms point to different tissues: hyaline refers to the smooth cartilage covering bone ends, fibrous describes fibrous connective tissues/ capsule, and tendinous relates to tendons. So the fluid responsible for lubrication is synovial fluid.