A noninvasive imaging technique for quantifying articular cartilage is needed for diagnosis, monitoring, and therapy control in osteoarthritis. In this study the accuracy of three-dimensional cartilage volume and thickness measurements in the knee with magnetic resonance imaging was analyzed. Eight cadaveric specimens had sagittal imaging with a fat suppressed gradient echo sequence. After a contrast agent was injected, two sagittal computed tomography data sets were obtained, with the knees being repositioned between the examinations. The cartilage thickness was determined, after three-dimensional reconstruction, using a minimal distance algorithm. The mean absolute volume deviation between magnetic resonance imaging and computed tomography arthrography was 3.3% and that between the two computed tomography data sets was 3.6%. The absolute error in determining the maximal cartilage thickness with magnetic resonance imaging was on average 0.6 intervals (of 0.5-mm thickness) and that between the computed tomography examinations was 0.5 intervals. In a patient with anterior knee pain, a focal cartilage defect was seen with magnetic resonance imaging, and this was verified by arthroscopic examination. Using three-dimensional image processing, magnetic resonance imaging can provide accurate data on cartilage volume and thickness in the human knee joint surfaces. This imaging technique potentially may be valuable in the treatment of patients with joint disease.