Purpose: In vivo measurement of the forces and strains in human tissues is currently impracticable. Computer modeling and simulation allows estimates of these quantities to be obtained noninvasively. This paper reviews our recent work on muscle, ligament, and joint loading at the knee during gait.
Methods: Muscle and ground-reaction forces obtained from a sophisticated computer simulation of walking were input into a detailed model of the lower limb to obtain ligament and joint-contact loading at the knee for one full cycle of gait.
Results: Peak anterior cruciate ligament (ACL) force occurred in early stance and was mainly determined by the anterior pull of the patellar tendon on the tibia. The medial collateral ligament was the primary restraint to anterior tibial translation (ATT) in the ACL-deficient knee. ATT in the ACL-deficient knee can be reduced to the level calculated for the intact knee by increasing hamstrings muscle force. Reducing quadriceps force was insufficient to restore ATT to the level calculated for the intact knee. For both normal and ACL-deficient walking, the resultant force acting between the femur and tibia remained mainly on the medial side of the knee. The knee adductor moment was resisted by a combination of muscle and ligament forces.
Conclusion: Knee-ligament loading during the stance phase of gait is explained by the pattern of anterior shear force applied to the leg. The distribution of force at the tibiofemoral joint is determined by the variation in the external adductor moment applied at the knee. The forces acting at the tibiofemoral and patellofemoral joints are similar during normal and ACL-deficient gait. Hamstrings facilitation is more effective than quadriceps avoidance in reducing ATT during ACL-deficient gait.
1Steadman-Hawkins Research Foundation, Biomechanics Research Laboratory, Vail, CO; 2Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX; and 3Department of Mechanical and Manufacturing Engineering, The University of Melbourne, Victoria, AUSTRALIA
Address for correspondence: Kevin Shelburne, PhD, Steadman-Hawkins Research Foundation, Vail, Colorado 81657; E-mail: firstname.lastname@example.org.
Submitted for publication January 2005.
Accepted for publication June 2005.
This work was supported in part by the Steadman-Hawkins Sports Medicine Foundation, the Department of Biomedical Engineering at The University of Texas at Austin, the Department of Mechanical Engineering at The University of Melbourne (Australia), the National Science Foundation Engineering Research Centers Grant EEC-9876363, and Sulzer Orthopedics Inc., Austin, Texas.
Based on the keynote delivered to the ACSM 2004 annual meeting: “Exploring Knee Mechanics with Modeling and Simulation.”