A total of 18 adult patients with torn menisci (outer 1/3, posterior horn, medial meniscus) will be recruited and randomly divided into three groups: A (n=6), implantation of PRF after partial menisectomy; B (n=6), implantation of PRF after partial menisectomy and suture; C (n=6), partial menisectomy only. All studied knee will be scanned on a 1.5-T MRI with surface coil at baseline before surgery, 3 months and 6 months and 12 months after surgery.