Hip joint contact force in the emu (Dromaius novaehollandiae) during normal level walking

Jessica E. Goetz, Timothy R. Derrick, Douglas R. Pedersen, Duane A. Robinson, Michael G. Conzemius, Thomas E. Baer, Thomas D. Brown

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


The emu is a large, (bipedal) flightless bird that potentially can be used to study various orthopaedic disorders in which load protection of the experimental limb is a limitation of quadrupedal models. An anatomy-based analysis of normal emu walking gait was undertaken to determine hip contact forces for comparison with human data. Kinematic and kinetic data captured for two laboratory-habituated emus were used to drive the model. Muscle attachment data were obtained by dissection, and bony geometries were obtained by CT scan. Inverse dynamics calculations at all major lower-limb joints were used in conjunction with optimization of muscle forces to determine hip contact forces. Like human walking gait, emu ground reaction forces showed a bimodal distribution over the course of the stance phase. Two-bird averaged maximum hip contact force was approximately 5.5 times body weight, directed nominally axially along the femur. This value is only modestly larger than optimization-based hip contact forces reported in literature for humans. The interspecies similarity in hip contact forces makes the emu a biomechanically attractive animal in which to model loading-dependent human orthopaedic hip disorders.

Original languageEnglish (US)
Pages (from-to)770-778
Number of pages9
JournalJournal of Biomechanics
Issue number4
StatePublished - 2008

Bibliographical note

Funding Information:
The authors have no conflict of interest to report. Funding for the research presented in this paper was provided by NIH Grant #AR 049919.


  • Contact forces
  • Emu
  • Gait analysis
  • Kinematics


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