Fig. 2
a–d Arthroscopic views of left ankle in a 54-year-old male patient who underwent marrow stimulation alone combined with supramalleolar osteotomy. e–h Arthroscopic views of the left ankle in a 52-year-old female patient who underwent mesenchymal stem cell injection and marrow stimulation combined with supramalleolar osteotomy. a, e Intraoperative arthroscopic findings showing a cartilage lesion with osteoarthritic change in the medial gutter area. b, f Arthroscopic views showing the perforation of the subchondral bone with a microfracture awl after the debridement of all unstable and damaged cartilage in the lesion. c, g Adequate bone bleeding at microfracture holes was confirmed after the tourniquet was released. d Second-look arthroscopy showing poor cartilage regeneration at the microfractured site (International Cartilage Repair Society [ICRS] grade IV). g Arthroscopic view after mesenchymal stem cell injection. h Second-look arthroscopy showing nearly normal coverage of the cartilage lesion (ICRS grade II)