Fig. 1.

(a) A 58-year-old woman had a lesion on the medial femoral condyle and a focal lesion on the medial tibial plateau of the left knee. (b) The damaged cartilage was completely removed, and the sclerotic subchondral bone was removed. Multiple holes with a diameter of 4 mm and 2 mm were created on the medial femoral condyle. (c) After a mixture of hyaluronic acid and human umbilical cord blood-derived mesenchymal stem cells was implanted in the holes and trimmed to the height of surrounding articular surface on the medial femoral condyle. (d) Second-look arthroscopy at 15 months after surgery. This was performed during opposite knee surgery.