A Combined Experimental and Computational Approach to Subject Specific Analysis of Knee Joint Laxity

Abstract

Modeling complex knee biomechanics is a continual challenge, which has resulted in many models of varying levels of quality, complexity, and validation. Beyond modeling healthy knees, accurately mimicking pathologic knee mechanics, such as after cruciate rupture or meniscectomy, is difficult. Experimental tests of knee laxity can provide important information about ligament engagement and overall contributions to knee stability for development of subjectspecific models to accurately simulate knee motion and loading. Our objective was to provide combined experimental tests and finiteelement (FE) models of natural knee laxity that are subjectspecific, have onetoone experiment to model calibration, simulate ligament engagement in agreement with literature, and are adaptable for a variety of biomechanical investigations (e.g., cartilage contact, ligament strain, in vivo kinematics). Calibration involved perturbing ligament stiffness, initial ligament strain, and attachment location until modelpredicted kinematics and ligament engagement matched experimental reports. Errors between modelpredicted and experimental kinematics averaged <2 deg during varus–valgus (VV) rotations, <6 deg during internal–external (IE) rotations, and <3 mm of translation during anterior–posterior (AP) displacements. Engagement of the individual ligaments agreed with literature descriptions. These results demonstrate the ability of our constraint models to be customized for multiple individuals and simultaneously call attention to the need to verify that ligament engagement is in good general agreement with literature. To facilitate further investigations of subjectspecific or population based knee joint biomechanics, data collected during the experimental and modeling phases of this study are available for download by the research community.