Synvisc Hylan GF 20 mg Injection is used in the treatment of osteoarthritis. Synvisc Hylan GF 20 mg Injection is natural polysaccharide (sugar). In bone disorders (osteoarthritis), it works by reducing friction in the joints and helps them work smoothly. Synvisc Hylan GF 20 mg Injection also has an antiageing effect. When injected into the skin (on the face most often), it works by hydrating the skin, enabling it to retain more water. This creates a filling/plumping effect and potentially fights wrinkles and other signs of ageing.