How to Boost Synovial Fluid and Support Healthy Joints Joint movement depends on synovial fluid, a slippery liquid that reduces friction and nourishes cartilage. This fluid is constantly renewed through joint movement and adequate water availability. When hydration is reduced, synovial Joint fluid fills the small space between the ends of bones and acts like a natural lubricant. The synovial membrane creates this thick, silky fluid using long molecules that hold water and give it a LUBRI JOINT