Related Experiment Video
Updated: May 8, 2026

An Inertial Measurement Unit Based Method to Estimate Hip and Knee Joint Kinematics in Team Sport Athletes on the Field
Published on: May 26, 2020
ACL forces and knee kinematics produced by axial tibial compression during a passive flexion-extension cycle
Keith L Markolf1, Steven R Jackson, Brock Foster
1Biomechanics Research Section, Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, 1000 Veteran Ave Room 21-67, Los Angeles, California.
Abstract:
Application of axial tibial force to the knee at a fixed flexion angle has been shown to generate ACL force. However, direct measurements of ACL force under an applied axial tibial force have not been reported during a passive flexion-extension cycle. We hypothesized that ACL forces and knee kinematics during knee extension would be significantly different than those during knee flexion, and that ACL removal would significantly increase all kinematic measurements. A 500 N axial tibial force was applied to intact knees during knee flexion-extension between 0° and 50°. Contact force on the sloping lateral tibial plateau produced a coupled internal + valgus rotation of the tibia, anterior tibial displacement, and elevated ACL forces. ACL forces during knee extension were significantly greater than those during knee flexion between 5° and 50°. During knee extension, ACL removal significantly increased anterior tibial displacement between 0° and 50°, valgus rotation between 5° and 50°, and internal tibial rotation between 5° and 15°. With the ACL removed, kinematic measurements during knee extension were significantly greater than those during knee flexion between 5° and 45°. The direction of knee flexion-extension movement is an important variable in determining ACL forces and knee kinematics produced by axial tibial force.
Related Concept Videos
Knee Joint
A total of seven ligaments support the knee joint. The patellar ligament, which is also attached to the quadriceps femoris group...
Muscles that Move the Leg
Anterior Compartment
The quadriceps femoris, the most visible muscle of the anterior compartment, is integral for leg extension and thigh flexion. It is formed by merging four distinct muscles — the vastus lateralis, vastus medialis, vastus intermedius, and rectus femoris. The quadriceps tendon, a shared tendon of the four quadriceps muscles, is affixed to...
Eccentric Axial Loading in a Plane of Symmetry
Bones of the Lower Limb: Femur and Patella
Ankle Joint
Axial and Appendicular Muscles
Axial Muscles
Axial muscles, situated along the body's midline, are intricately connected to the axial skeleton, which includes the skull, spine, ribs, and sternum. These muscles facilitate facial expressions and play a...

