Autologous chondrocyte implantation compared with microfracture in the knee - a randomized trial. - Knutsen,G.; Engebretsen,L.; Ludvigsen,T.C.; Drogset,J.O.; Grontvedt,T.; Solheim,E.; Strand,T.; Roberts,S.; Isaksen,V.; Johansen,O. (J Bone Joint Surg [Am], 2004)