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 Natural Joint Lubrication: How to Keep Your Joints Healthy Liv Hospital Promoting Synovial Fluid Production for Better Joint Health 7 Ways to Lubricate Joints Naturally for Less Pain Knee Osteoarthritis: Early Signs, Causes, Diagnosis, Treatment