Intro: Platelet rich plasma (PRP) is largely used in various musculoskeletal disorders such as chronic tendinopathies but also osteoarthritis (OA). Several therapeutic trials evaluating the effectiveness of intra-articular PRP injections in knee OA as well as meta-analyses have already been published. Most of them have compared PRP to Hyaluronic Acid (HA). Their design was very heterogeneous in terms of PRP characteristics and injection protocol. Moreover, the number of patients included was often very low. Only few studies have compared PRP to placebo (physiological serum) and presented the same methodological limitations (limited number of patients, heterogeneous protocols in terms of number and frequency of injections, characteristics of PRP, etc.). Given the insufficient level of evidence related to these limitations, PRP injections are not recommended in the treatment of symptomatic knee OA by the main scientific societies such as American College of Rheumatology (ACR), Osteoarthritis Research Society International (OARSI), American Academy of Orthopedic Surgeons (AAOS) and French Society of Rheumatology (SFR). Experts in the field agree on the need for a placebo-controlled trial with hihg methodological quality and simple design in order to conclude with a good level of evidence to the benefit or not of this new therapeutic weapon in symptomatic knee osteoarthritis of moderate radiographic severity.