Development and validation of a kinematically-driven discrete element model of the patellofemoral joint

Jonathan A. Gustafson*, John J. Elias, Richard E. Debski, Shawn Farrokhi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Quantifying the complex loads at the patellofemoral joint (PFJ)is vital to understanding the development of PFJ pain and osteoarthritis. Discrete element analysis (DEA)is a computationally efficient method to estimate cartilage contact stresses with potential application at the PFJ to better understand PFJ mechanics. The current study validated a DEA modeling framework driven by PFJ kinematics to predict experimentally-measured PFJ contact stress distributions. Two cadaveric knee specimens underwent quadriceps muscle [215 N]and joint compression [350 N]forces at ten discrete knee positions representing PFJ positions during early gait while measured PFJ kinematics were used to drive specimen-specific DEA models. DEA-computed contact stress and area were compared to experimentally-measured data. There was good agreement between computed and measured mean and peak stress across the specimens and positions (r = 0.63–0.85). DEA-computed mean stress was within an average of 12% (range: 1–47%)of the experimentally-measured mean stress while DEA-computed peak stress was within an average of 22% (range: 1–40%). Stress magnitudes were within the ranges measured (0.17–1.26 MPa computationally vs 0.12–1.13 MPa experimentally). DEA-computed areas overestimated measured areas (average error = 60%; range: 4–117%)with magnitudes ranging from 139 to 307 mm 2 computationally vs 74–194 mm 2 experimentally. DEA estimates of the ratio of lateral to medial patellofemoral stress distribution predicted the experimental data well (mean error = 15%)with minimal measurement bias. These results indicate that kinematically-driven DEA models can provide good estimates of relative changes in PFJ contact stress.

Original languageEnglish
Pages (from-to)164-172
Number of pages9
JournalJournal of Biomechanics
StatePublished - 9 May 2019
Externally publishedYes


  • Discrete element analysis
  • Joint contact
  • Modeling
  • Patellofemoral
  • Stress


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