Platelet-rich plasma (PRP) is an autologous product prepared from the patient's own blood, representing a powerful source of platelet-derived growth factors, particularly useful in the field of regenerative medicine. The active and sequential secretion of these growth factors induces different cell signaling cascades that activate angiogenesis, cell proliferation, cell differentiation, eventually leading to new matrix synthesis and tissue regeneration.

The potential benefits from the use of PRP for the treatment of cartilage defects rely on a number of studies conducted in validated animal models or in vitro, demonstrating the ability of PRP to stimulate collagen production and proteoglycans synthesis, as well as the proliferation and differentiation of mesenchymal stem cells into chondrocytes. Additionally, an increasing number of clinical studies shows an improvement of symptoms, most especially pain, without any occurrence of serious adverse events.

Hyaluronic acid (HA), as one of the major components of the synovial fluid surrounding the cartilage, assumes an important role in the viscoelastic properties of the articular cartilage, conferring its shock absorbing and lubricating functions.

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.

Cellular MatrixTM is a CE-marked class III medical device manufactured by the Swiss company RegenLab SA. Cellular MatrixTM allows to prepare autologous PRP combined with a non-crosslinked hyaluronic acid in a safe, rapid manner and in a single step. The PRP/HA combination is intended to be injected intra-articularly, in order to relieve osteoarthritic symptoms and to improve joint mobility and function. Therefore, the PRP/HA combination might represent a novel therapeutic option for patient suffering from knee osteoarthritis.

This study will evaluate whether the effects of a PRP/HA combination prepared with Cellular Matrix™, when injected intra-articularly for the treatment of mild to moderate knee osteoarthritis, are superior to those of a well-recognized hyaluronic acid treatment (Ostenil® Plus), on one hand, and to those of PRP alone, on the other hand.