title: How tibiofemoral alignment and contact locations affect predictions of medial and lateral tibiofemoral contact forces.
abstract: Understanding degeneration of biological and prosthetic knee joints requires knowledge of the in-vivo loading environment during activities of daily living. Musculoskeletal models can estimate medial/lateral tibiofemoral compartment contact forces, yet anthropometric differences between individuals make accurate predictions challenging. We developed a full-body OpenSim musculoskeletal model with a knee joint that incorporates subject-specific tibiofemoral alignment (i.e. knee varus-valgus) and geometry (i.e. contact locations). We tested the accuracy of our model and determined the importance of these subject-specific parameters by comparing estimated to measured medial and lateral contact forces during walking in an individual with an instrumented knee replacement and post-operative genu valgum (6°). The errors in the predictions of the first peak medial and lateral contact force were 12.4% and 11.9%, respectively, for a model with subject-specific tibiofemoral alignment and contact locations determined through radiographic analysis, vs. 63.1% and 42.0%, respectively, for a model with generic parameters. We found that each degree of tibiofemoral alignment deviation altered the first peak medial compartment contact force by 51N (r(2)=0.99), while each millimeter of medial-lateral translation of the compartment contact point locations altered the first peak medial compartment contact force by 41N (r(2)=0.99). The model, available at www.simtk.org/home/med-lat-knee/, enables the specification of subject-specific joint alignment and compartment contact locations to more accurately estimate medial and lateral tibiofemoral contact forces in individuals with non-neutral alignment.
authors.affiliation: School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA. Electronic address: Zach.Lerner@ColoState.edu.
authors.forename: Zachary F
authors.initials: ZF
authors.lastname: Lerner
authors.affiliation: Departments of Bioengineering and Mechanical Engineering, Stanford University, Stanford, CA, USA.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: DeMers
authors.affiliation: Departments of Bioengineering and Mechanical Engineering, Stanford University, Stanford, CA, USA.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Delp
authors.affiliation: School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA; Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA.
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Browning
mesh_terms: D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena / Q000502:physiology; D017760:Bone Malalignment / Q000473:pathology / Q000517:prevention & control*; D005269:Femur / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D056304:Genu Valgum / Q000473:pathology; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D008297:Male; D055595:Mechanical Phenomena; D008954:Models, Biological; D009142:Musculoskeletal Physiological Phenomena; D011859:Radiography; D013314:Stress, Mechanical; D013977:Tibia / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D016138:Walking / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology
keywords: Joint loading; Musculoskeletal modeling; Osteoarthritis; Tibiofemoral contact force; Walking