title: Unified quantification of variation in passive knee joint constraint.
abstract: The interrelationship that exists between multiple degrees of freedom to produce a net constraint across the range of passive motion of the knee is not fully understood. Manual joint laxity assessments were performed on 28 cadaveric specimens and used to develop a unified description of the passive laxity envelope that incorporated multiple degrees of freedom into a single analysis using radial basis functions. The unified envelopes were then included in a principal component analysis to identify the primary modes of variation. The first three modes of variation constituted 82% of the variation. The first principal component (36.5% explained variation) correlated with changes to the relationship between varus-valgus and internal-external rotation and had the largest impact on internal-external laxity. The second principal component (27.2% explained variation) correlated with a shift in the internal-external envelope. The third principal component (18.3% explained variation) correlated with a shift in the varus-valgus envelope and a change in varus-valgus laxity. This research presents a novel methodology for quantifying complex changes to passive knee constraint, which may be used as a means for objectively scoring joint laxity and evaluating complex relationships between degrees of freedom in a single analysis.
authors.affiliation: BioEngineering Graduate Program, University of Kansas, Lawrence, KS, USA.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Cyr
authors.affiliation: BioEngineering Graduate Program, University of Kansas, Lawrence, KS, USA Department of Mechanical Engineering, University of Kansas, Lawrence, KS, USA maletsky@ku.edu.
authors.forename: Lorin P
authors.initials: LP
authors.lastname: Maletsky
keywords: Knee; laxity; passive constraint; principal component analysis; radial basis function