Knee Osteoarthritis: Early Signs, Causes, Diagnosis, Treatment 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 Gel Knee Injections for Pain Relief What to Expect Oak Brook Medical Promoting Synovial Fluid Production for Better Joint Health Gel injections (also called viscosupplementation) are used to treat joint pain from arthritis, especially in the knee. The gel acts as a lubricant and shock absorber inside the joint, helping reduce friction,