Cruciate ligaments: evaluation by magnetic resonance imaging and anatomy. Magnetic resonance imaging (MRI) is one of the most common imaging techniques used in the evaluation of the cruciate ligaments. The aim of this study was to assess the MR images of the cruciate ligaments in different populations. MR images of the cruciate ligaments were obtained in 50 volunteers. Images were also obtained of 30 knee specimens with a high-resolution 1.5-T MR unit. The thickness of the ligaments was measured at the attachments to the femur and tibia. The anterior cruciate ligament was thickest at its femoral attachment and the posterior cruciate ligament was thickest at its tibial attachment. The thickness of the medial collateral ligament was 3-4 mm and that of the lateral collateral ligament was 1-2 mm at both its femoral and tibial attachments. At each joint, the thickness of the anterior cruciate ligament was greater than that of the posterior cruciate ligament, and both were greater than that of the medial collateral ligament. The thickness of the posterior cruciate ligament was found to be greater than that of the medial collateral ligament at its tibial attachment. The thickness of the anterior cruciate ligament was greater at its femoral attachment, but the posterior cruciate ligament was thicker at its femoral attachment. The thickness of the medial collateral ligament did not change according to the presence or absence of cartilage degeneration of the knee. In a nonpathologic knee, the anterior cruciate ligament is thicker at its femoral attachment. The posterior cruciate ligament is thicker at its tibial attachment and the medial collateral ligament is thicker at its femoral attachment. Further studies on the anatomy and biomechanics of the cruciate ligaments are needed to increase the knowledge about these ligaments.