Comparative study of the size and shape of human anterior and posterior cruciate ligaments

Abstract

As an important step toward determination of the function of cruciate ligaments, the cross‐sectional shapes and areas of the anterior cruciate, posterior cruciate, and meniscofemoral ligaments were evaluated in situ within the same knee with use of a laser micrometer system. Measurements were made in eight human cadaveric knees at five levels along the midsubstance of each ligament, with the knee at 0°, 30°, 60°, and 90° of flexion. The posterior cruciate ligament was found to be widest in the medial‐lateral direction, whereas the anterior cruciate ligament usually was larger in the anterior‐posterior direction. The cross‐sectional shapes of the anterior cruciate ligament generally were noted to be more circular along the entire midsubstance than were those of the posterior cruciate ligament. In contrast, the cross‐sectional shapes of the posterior cruciate ligament were more circular near the tibia, becoming progressively more elongated toward the femur. The meniscofemoral ligaments were more circular than the cruciate ligaments, with an occasional medial‐lateral widening similar to that of the posterior cruciate ligament. The cross‐sectional area of both the cruciate ligaments changed along the length of the midsubstance, with the anterior cruciate ligament becoming slightly larger distally and the posterior cruciate ligament enlarging proximally. The angle of flexion of the knee was not found to have a significant effect on the cross‐sectional areas of the ligaments but was noted to alter the cross‐sectional shapes. Using within‐specimen comparisons, the cross‐sectional area of the posterior cruciate ligament was found to be approximately 1.5 times larger than that of the anterior cruciate ligament at the proximal and midsubstance levels but was only 1.2 times larger at the most distal level. The total cross‐sectional area of the meniscofemoral ligaments was approximately 22% that of the posterior cruciate ligament.