American Journal of Sports Medicine

Christopher D. Harner M.D., John W. Xerogeanes M.D., Glen A. Livesay M.S., Gregory J. Carlin B.S., Brian A. Smith M.D., Takeshi Kusayama M.D., Shinji Kashiwaguchi M.D., and Savio L-Y. Woo Ph.D.


This purpose of this research was to study in detail the structural and functional properties of the human PCL complex (Anterolateral [AL] and posteromedial [PM] components of the PCL and the meniscofemoral [MFL] ligaments). Anatomical properties included in-situ cross-sectional data of the ligaments and their insertions. The corresponding ACL from each knee was also measured for comparison. From the anatomical data we then proceeded with determining the structural properties of each individual component of the PCL complex.

Cross-sectional anatomy was measured using a laser micrometer system. Eight cadaver knees were used to measure the ligament cross-sectional shape and area from the tibia to the tibia along the ACL, PCL and MFL. The PCL increased in cross-sectional area from tibia to femur and the ACL from femur to tibia. The MFLs did not change in their course from the lateral meniscus to the femoral insertions. The PCL cross-sectional area was approximately 150% of the ACL proximally (femoral) and 120% distally (tibial). The MFLs averaged approximately 22% of the entire cross-sectional area of the PCL. Knee flexion angle did not significantly affect the cross-sectional areas.

The insertion sites of the PCL and ACL were examined using a 3D digitizing system to record the coordinates of the periphery of each insertion. The insertion sites of the ACL and PCL were 300-500% larger than the cross-section of their respective midsubstance.

In the final section of our anatomical analysis we determine through transmission electron microscopy fibril size within the ACL and PCL complex from proximal (femoral) to distal (tibial). This data revealed that the fibril size within the PCL becomes increasingly larger from tibial to femoral insertions, while those of the ACL do just the opposite. The mean collagen fibril areas within the MFLs were found to be relatively uniform throughout the ligament. The mean collagen fibril size within the MFL was significantly larger than both the ACL and PCL.

The biomechanical properties of the femur-PCL-tibia complex were evaluated using 14 additional human cadaver knees. The PCL was divided into two functional components, the AL which is taut in knee flexion, the PM which is taut in knee extension. The AL had a significantly greater linear stiffness and ultimate load than both the PM and MFL. The AL and MFL displayed similar elastic moduli which were both significantly greater than that of the PM.

This inclusive study provides a more complete understanding of the unique anatomical and biomechanical properties of the PCL complex. Knowledge of the biomechanical properties and anatomy of the PCL complex will be an aid to graft material selection and placement.