Treatment The surgical procedure will be executed as following: the day before the surgery 120 ml of venous blood will be collected for the platelet gel production performed with an automatic method by Unit 5. The day of the surgery, 60 ml of bone marrow will be aspirate from the posterior iliac crest of the patient and concentrated directly in the operating room by a specific device (kit IOR-G1, Novagenit, Mezzolombardo, TN, Italy), in order to obtain 6 mL of concentrate bone marrow (CBM) containing nucleated cells (stem cells, monocytes, lymphocytes, and other bone marrow resident cells). After the bone marrow harvesting phase, a standard ankle arthroscopy will be performed, with the patient in the supine position. The lesion will be detected and cleaned.