It was conducted a prospective study with a series of 153 patients treated with PRP injections in patient affected by knee osteoarthritis. One independent observer performed clinical and functional evaluations at T0 (recruitment), T1 (one month after the injection), T2 (three months after the last injection) and T3 (six months after the last injection).

The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Knee Score Society (KSS) score and the Visual Analogue Scale (VAS) were evaluated and recorded for each patient at each follow up.

Inclusion Criteria:

• Age between 40 and 81;
• Body mass index (BMI) between 21.5 and 29.3;
• Chronic history (for at least 4 months) of knee joint pain;
• Radiographically documented knee osteoarthritis of grades 1 to 3 (Kellgren-Lawrence (K-L) radiographic classification scale)

Exclusion Criteria:

• Radiographically severe documented knee osteoarthritis of grade 4 (K-L radiographic classification scale);
• Previous femur and tibia fractures;
• Knee previous surgical treatment (e.g., arthroscopy);
• Hyaluronic acid infiltration within the previous six months;
• Hemoglobin levels <10 g/dL;
• History of oncohematological disease, infections, or immunodepression

One hundred and fiftythree patients referring to the Orthopaedic and Trauma Unit of the local University Hospital between January 2018 and January 2020 with knee osteoarthritis