The purpose of this study is to compare the efficacy of platelet-rich plasma versus hyaluronic acid intra-articular injections for the treatment of osteoarthritis of knee joint.

The hypothesis is that PRP intra-articular injection is comparable or even better than hyaluronic acid injection.

Osteoarthritis (OA) has a significant impact on our society. The limited regenerative capacity of cartilage is part of this problem. Existing degenerative lesions lead to accelerated deterioration of the articular (joint) surface leading to end-stage arthritis. In particular, the most recent knowledge regarding tissue biology highlights a complex regulation of growth factors (GFs) for the normal tissue structure and the reaction to tissue damage. The influence of GFs on cartilage repair is now widely investigated in vitro and in vivo. Platelet Rich Plasma (PRP) is a simple, low- cost and minimally- invasive method that allows one to obtain a natural concentrate of autologous GFs from the blood, and it is increasingly applied in the clinical practice to treat knee degenerative pathology, such as chondropathy and early OA. The biological rational of PRP is that platelets contain storage pools of GFs, cytokines, chemokines and many other mediators.Although its widespread application, there are little high level studies in the literature to demonstrate the real efficacy of PRP.

The investigators hypothesized that intra-articular injections of PRP to treat knee osteoarthritis could determine pain relief and recovery of knee function with overall clinical outcome comparable or even better than viscosupplementation, which is a common injective approach applied in this kind of pathology. To this purpose the investigators designed a double blind randomized controlled trial comparing PRP vs viscosupplementation.

Inclusion Criteria:

• Patients with osteoarthritis of knee (by American College of Rheumatology Criteria) and Kellgren-Lawrence grade I ~ III
• More than 40 out of 100-mm VAS scale for pain at screening and baseline
• Participant is willing and able to give informed consent for participation in the study

Exclusion Criteria:

• Patients with Hb values < 10 g/dl and platelet values < 100,000/ul
• Patients with a current or medical history of autoimmune disease
• Recent fever ( within 2 weeks) or serious illness
• Local infection at the site of the procedure
• Corticosteroid injection at treatment site within 1 month
• Systematic use of corticosteroids within 2 weeks
• Female participants who are pregnant, lactating or planning pregnancy during the course of the study
• Patients who have been administered with immunosuppressants within the past 6 weeks
• Patients who are enrolled in any other clinical trials within 4 weeks
• Patients who the principal investigator considers inappropriate for participation in the clinical trial for reasons other than those listed above