Abstract
The objective of this study was to examine the state of stress within the solid matrix
of articular cartilage in the patellofemoral joint, using anatomically faithful biphasic
models of the articular layers, with the joint subjected to physiologic muscle force
magnitudes. Finite element models of five joints were created from human cadaver knees.
Biphasic sliding contact analyses were performed using FEBio software to analyze the
response of the joint from 30 to 60 degrees of knee flexion. Results demonstrated
that the collagen matrix always sustains tensile stresses, despite the fact that the
articular layers are loaded in compression. The principal direction of maximum solid
stresses was consistent with the known orientation of collagen fibrils in cartilage.
The magnitudes of these tensile stresses under muscle forces representative of activities
of daily living were well below tensile failure stresses reported in the prior literature.
Results also hinted that solid matrix stresses were higher in the patellar versus
femoral superficial zone. These anatomically correct finite element models predicted
outcomes consistent with our understanding of structure-function relationships in
articular cartilage, while also producing solid matrix stress estimates not observable
from experiments alone, yet highly relevant to our understanding of tissue degeneration.
Keywords
cartilage mechanics - fibrous tissue - finite element analysis - biphasic contact
