a IKDC score regarding period of symptoms (pos) (A: pos ≤ 12 months, B: 12 months < pos < 60 months, C: pos ≥ 60 months). Graph shows IKDC score preoperatively and at three, six, 12 and 36 months. b Graph showing the influence of defect size (ds) (A: ds ≤ 4 cm2, B: 4 cm2< ds ≤ 6 cm2, C: ds >6 cm2) regarding IKDC score preoperatively and at three, six, 12 and 36 months