Journal of Biomechanics

Theodore W. Rudy, Mastaka Sakane, Richard E. Desbki, Savio L-Y. Woo


Coupled axial tibial rotation in rsponse to an anterior tibial load has been used as a common diagnostic measurement and as a measn to load the ligamentous structures during laboratory tests. However, the exact location of the point of application of these loads as well as the corresponding sensitivity of the coupled tibial rotation to this point can have an effect on the function of the soft tissues at the joint. Therefore , the purpose of this study was to determine the effects of four different points of application of the anterior tibial load on anterior tibial translation and coupled axial tibial rotation. The four points include: 1) geometric point Ğmidway between the collateral ligament insertion sites on the tibia 2) clinical point-a position that attempts to simulate clinical daignstic tests, 3) medial point-a position medial to the geometric point and 4) lateral point Ğa position lateral to the clinical point. A robotic/universal force-moment sensor testing system was used to apply the anterior tibial load at the four points of application and to record the resulting joint motion. Anterior tibial translation in response to an anterior tibial load of 100 N was found not to vary between the four points of application of th anterior tibial load at all flexion angles examined. However, internal tibial rotation was found for the lateral point (13 ± 10° at 30° of knee flexion) in all specimens and clinical point (8 ± 10° and 30° of knee flexion) while external rotation resulted whenthe load was applied at the medial point (-8 ± 7° at 30° of knee flexion). Both internal and external tibial rotations occurred throughout the range of flexion when the tibial load was applied at the geometric point. The results suggest that the clinical point should be used as the point of application of the anterior of the anterior tibial load whenever clinical examinations are simulated and multi-degree-of Ğfreedom joint and soft tissue function are examined.