Joint angles calculated from 3D joint positions during a portion of the same walking bout shown in <b>Fig. 5</b>.

<p>As in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013617#pone-0013617-g008" target="_blank">Fig. 8</a>, the colored points represent successive frames of tracked video. The gray boxes indicate the stance phase of each stride, defined using the <i>z</i>-position of the TiTa point. The FTi joint angle (blue) was estimated using the CTr, FTi, and TiTa points. The TrF joint angle (pink) was estimated using the CTr-FTi-TiTa plane and the coxal plane. The CTr angle (black) was estimated using the ThC, CTr, and FTi points. The angle of the coxa in the <i>xz</i>-plane centered at the ThC position was used to define the motion in the first degree of freedom (promotion/remotion) of the ThC joint (ThC₁, green), and the declination of the coxa from the <i>xy</i>-plane determined its motion in the ThC joint's second degree of freedom (ThC₂, orange).