Fifty consecutive and strictly selected patients, affected by Grade II or III chondromalacia, underwent one year treatment (9 injections) with autologous PRP in a liquid form with 2,0 to 2,5-fold platelets concentration. Outcome measures included hte Lysholm, Tegner, IKDC, and Cincinnati scores. Magnetic resonance imaging was used to evaluate cartilage thickness and degree of degeneration.