The aim of this experimental animal study was to compare histologically and immunohistochemically knee cartilage appearances after cartilage resurfacing of iatrogenic de- fects with biosynthetic plug, autograft or conservative approach. Thirty New Zealand White rabbits were used. A full-thickness cylindrical defect of the femoral groove of 4,5mm x 7mm was created with a hand drill. In Group A the defect was repaired with a bone graft substitute (BGS) plug, in Group B with an osteochondral autograft, while in Group C rabbits were left untreated. 24 weeks postoperatively, smooth articular was found macroscopically in some trocleasâ€™ surfaces; in all others, an articular surface with discontinuities was ob- served. Histology revealed many statistical differences between the groups as far as the ICRS categories are concerned. In particular, the mean scores were for the BGS group 1,2Â±1,55 (surface), 1,6Â±1,35(matrix), 0,7Â±0,82 (cell distribution), 3 (cell viability), 1,4Â±0,84 (subchondral bone) and 1,2Â±1,55 (cartilage mineralization). The values for the autograft group were 1,5Â±1,58, 3,2,3,2,3 respectively. The control group received the following val- ues respectively: 0,9Â±1,45, 0,7Â±0,67, 0,1Â±0,32, 2,6Â±0,84, 0,9Â±1,19, 0,6Â±1,26. Immunofluo- resence also revealed many differences. In group A, six specimens were found with collagen II. All specimens of group B revealed to have collagen II, while the control group only one specimen was found with collagen II. We found statistical differences as far as the matrix, cell distribution, subchondral bone and cartilage mineralization ICRS categories are concerned. Group B received the best scores, while group A was second; the control group got the worst ICRS scores in these categories. The treatment of osteochondral lesions is better amended with osteochondral autograft rather than with synthetic BGS implants.