A gel injection for the knee is often used when the joint loses some of its natural lubrication, which can happen with arthritis or cartilage wear., The gel acts as a lubricant and shock absorber Hyaluronic Acid Injections for Knee Osteoarthritis: What to Expect: Cascade Orthopedics & Sports Medicine Center, P.C.: Orthopedic Surgery How GELSYN 3 works Bioventus OA Knee Pain Relief A knee gel injection is used to improve lubrication inside the joint. In conditions like osteoarthritis, the natural synovial fluid that helps the knee glide smoothly can lose its protective