The present invention concerns amide derivatives of hyaluronic acid (HA) and biomaterials made of amide derivatives of hyaluronic acid (HA), particularly the hexadecylamide of HA, administered by the intra-articular route as a partial/total substitute for synovial fluid to treat joints affected by osteoarthrosis (OA) as well as cases of joint inflammation and/or trauma that cause damage to the cartilage and/or synovia (associated with pain).Lastly, we describe and claim their use in the treatment of joints where the entire structure shows signs of wear due to physiological aging.