Knee joint mechanics - assessment and modeling

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The loss of integrity or reconstruction of the anterior cruciate ligament (ACL) in the knee can also alter joint stability and dynamics and lead to higher risk and incidence of osteoarthritis (OA). However, direct non-invasive in-vivo quantification of joint contact mechanics within the joint structures has been limited. Consequently, characteristics of normal healthy joint mechanics, and those leading to pathological conditions are not well established. Further, the optimal criteria and treatments for reconstruction of joint structures to re-establish pre-injury joint mechanics are also lacking. The overall research goals are to understand relations amongst joint mechanics, joint health status, joint injury and repair mechanisms, and the development of degenerative changes associated with ligament injury and repair. Two main hypotheses will be tested: (H1) Joint malalignment, ACL deficiency and reconstruction result in perturbed joint mechanics, and (H2) an optimal geometry and dynamic control exists for an ACL reconstruction surgery that re-establishes normal knee joint kinematics and kinetics. Knee joint contact and tissue characteristics will be imaged and quantified for 4 in-vivo groups: healthy, OA, ACL deficient and ACL reconstructed under various knee flexion and loading conditions. Using novel image registration techniques, normative ranges for tissue characteristics will be developed. Joint dynamic stability will be assessed for each group using 3D motion analysis, linked to MR images of joint structure using common reference markers, EMG and helical axis analysis. A 3D knee joint model over a dynamic range of motion will be constructed including. subject specific bony segments, skeletal muscles, and passive tissues. Kinematic and kinetic relationships between structures will be established using principles of multibody dynamics and optimization. The validated 3D numerical model will be applied to evaluate the influence of ligament reconstruction variables on joint dynamics and function. This research will generate a more comprehensive understanding of changes in joint mechanics due to compromises of knee structure, thus enhancing our ability to design effective diagnoses, treatments and devices for joint health.