Trabecular bone in the bird knee responds with high sensitivity to changes in load orientation

H. Pontzer, D. E. Lieberman, E. Momin, M. J. Devlin, J. D. Polk, B. Hallgrímsson, D. M.L. Cooper

Research output: Contribution to journalArticlepeer-review


Wolff's law of trajectorial orientation proposes that trabecular struts align with the orientation of dominant compressive loads within a joint. Although widely considered in skeletal biology, Wolff's law has never been experimentally tested while controlling for ontogenetic stage, activity level, and species differences, all factors that may affect trabecular bone growth. Here we report an experimental test of Wolff's law using a within-species design in age-matched subjects experiencing physiologically normal levels of bone strain. Two age-matched groups of juvenile guinea fowl Numida meleagris ran on a treadmill set at either 0° (Level group) or 20° (Incline group), for 10 min per day over a 45-day treatment period. Birds running on the 20° inclined treadmill used more-flexed knees than those in the Level group at midstance (the point of peak ground reaction force). This difference in joint posture enabled us to test the sensitivity of trabecular alignment to altered load orientation in the knee. Using a new radon transform-based method for measuring trabecular orientation, our analysis shows that the fine trabecular bone in the distal femur has a high degree of correspondence between changes in joint angle and trabecular orientation. The sensitivity of this response supports the prediction that trabecular bone adapts dynamically to the orientation of peak compressive forces.

Original languageEnglish (US)
Pages (from-to)57-65
Number of pages9
JournalJournal of Experimental Biology
Issue number1
StatePublished - Jan 2006
Externally publishedYes


  • Biomechanics
  • Guinea fowl
  • Knee joint
  • Skeletal biology
  • Trabecular bone
  • Wolff's law

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science


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