PurposeSevere symptomatic and unstable osteochondral defects of the knee are difficult to treat. A variety of surgical techniques have been developed. However, the optimal surgical technique is still controversial. We present a novel technique in which autologous bone grafting is combined with gel-type autologous chondrocyte implantation (GACI).MethodsIsolated severe osteochondral defects of the medial or lateral femoral condyle were treated by a two-step procedure. Firstly, chondrocytes were harvested during arthroscopy and cultured for 6 weeks. Secondly, a full thickness corticospongious autologuos bone graft, harvested from the medial or lateral femur condyle, is impacted in the defect and covered by GACI. The fibrin gel fills up to the exact shape of the chondral lesion and polymerizes within 3 min after application.ResultsFrom 2009 to 2011, 9 patients, median age 35 years (range 23–47), were treated by the combined autologous bone grafting and GACI technique. Median defect size was 7.1 cm2 (range 2.5–12.0), and median depth of the lesion was 0.9 cm (range 0.8–1.2). Median follow-up was 9 months (range 6–12 months). Six patients were available for 12-month follow-up. The mean IKDC score showed a 6-month improvement from 35 (SD ± 16) to 51 (SD ± 18) (n = 9; p = 0.01), and a 1-year improvement from 35 (SD ± 16) to 57 (SD ± 20) (n = 6; p = 0.03). The mean KOOS improved from 44 (SD ± 16) to 62 (SD ± 19) (n = 9; p = 0.07) at 6-month follow-up and from 44 (SD ± 16) to 65 (SD ± 24) (n = 6; p = 0.1) at 12-month follow-up. There was one failure that needed conversion to a unicompartmental knee arthroplasty.ConclusionCombined autologous bone grafting and GACI may offer an alternative surgical option for severe and unstable osteochondral defects of the knee.Level of evidenceIV.