 It was demonstrated that rheological properties of synovial fluid decrease with aging and in patients suffering from osteoarthritis. Nowadays, intra-articular injections of hyaluronic acid represent a well recommended therapeutic option to relieve osteoarthritic symptoms, conferring a mechanical action on joints structures, thus leading to reduced pain and improved joint function Based on these data, it seems reasonable to hypothesize that a combination of both PRP and hyaluronic acid could provide greater benefits compared to the administration of each product alone, as their effects on osteoarthritis improvement are based on different mechanisms of action. In fact, on one side PRP promotes cartilage regeneration, while on the other side the HA acts as 3-dimensional support mesh for PRP, providing optimal release of platelets growth factors, strengthening and extending in time the activity of PRP. 