New equations to calculate 3D joint centres in the lower extremities

Martin Sandau, Rikke V Heimbürger, Chiara Villa, Karl E Jensen, Thomas B Moeslund, Henrik Aanæs, Tine Alkjær, Erik B. Simonsen

Research output: Contribution to journalJournal articleResearchpeer-review


Biomechanical movement analysis in 3D requires estimation of joint centres in the lower extremities and this estimation is based on extrapolation from markers placed on anatomical landmarks. The purpose of the present study was to quantify the accuracy of three established set of equations and provide new improved equations to predict the joint centre locations. The 'true' joint centres of the knee and ankle joint were obtained in vivo by MRI scans on 10 male subjects whereas the 'true' hip joint centre was obtained in 10 male and 10 female cadavers by CT scans.

For the hip joint the errors ranged from 26.7 (8.9) to 29.6 (7.5) mm, for the knee joint 5.8 (3.1) to 22.6 (3.3) mm and for the ankle joint 14.4 (2.2) to 27.0 (4.6) mm. This differed significantly from the improved equations by which the error for the hip joint ranged from 8.2 (3.6) to 11.6 (5.6) mm, for the knee joint from 2.9 (2.1) to 4.7 (2.5) mm and for the ankle joint from 3.4 (1.3) to 4.1 (2.0) mm. The coefficients in the new hip joint equations differed significantly between sexes. This difference depends on anatomical differences of the male and female pelvis.
Original languageEnglish
JournalMedical Engineering & Physics
Issue number10
Pages (from-to)948-955
Publication statusPublished - 2015


  • Gait
  • Biomechanics
  • Conventional Gait Model
  • Marker set
  • Motion capture
  • Motion analysis


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