Cartilage defects that are less than 2cm squared are best treated with mircofracture surgery. This procedure has been successfully used to treat cartilage defects for many years and gives a predictable fibrocartilage repair tissue and excellent symptom relief for 7-10 years. 
The surgery involves creating a stable sided contained defect with no loose cartilage flaps, the base of the defect is penetrated to allow the underlying bone to bleed and form a blood clot in the crater. This blood clot matures over the next 3-6 months to form a fibriocartilage cap that covers the defect.
Bleeding microfracture holes

Healed microfracture