Assessment of surgically repaired cartilage lesions with stan- dardized cartilage sensitive magnetic resonance imaging was done to evaluate the integrity, morphologic features, and sig- nal of the articular surface, thereby obtaining information about the natural history of these procedures in the knee. Magnetic resonance imaging also assessed the interface be- tween the repaired and native cartilage, changes in the sub- chondral bone, and the appearance of cartilage over the op- posite and adjacent (native) surfaces. One hundred eighty magnetic resonance imaging examinations were obtained in 112 patients who had cartilage-resurfacing procedures, in- cluding 86 microfractures and 35 autologous chondrocyte implantations, at a mean of 15 and 13 months after surgery, respectively. Autologous chondrocyte implantations showed consistently better fill of the defects at all times compared with microfracture. The graft hypertrophied in 63% of sur- geries. The repair cartilage over the microfracture generally was depressed with respect to native cartilage. Propensity for bony overgrowth was most marked in the microfracture group, with loss of adjacent cartilage evident with progres- sive followup.