Fig. 5

Continuous Relative Phase (CRP) plots. Both groups had nearly identical shank-foot coupling in the surgical limb which is to be expected given the passive ankle joint of the prosthesis, which cannot be actively controlled. The thigh-shank coupling of the surgical limb highlights the level of dysfunction (low dynamic peak range) in the ‘low’ knee functioning group as the segments are almost completely in phase (rotated in same direction at same rate) the entire stride whereas the ‘high’ knee functioning group exhibits more anti-phase behavior with the thigh leading the shank similar to optimal functioning thigh-shank coupling (see intact limb Fig. 3). The pelvis-thigh coupling of the surgical limb also demonstrated differences between groups with the ‘high’ group exhibiting more variability in coordination strategy at load acceptance (1–30% of gait cycle) and swing (~ 55–100% of gait cycle). Variability across ‘high’ functioning participants was constrained during propulsive phase (~ 30–60% of gait cycle). Conversely, the ‘low’ group had more variability during propulsive phase and early swing. For the shank-foot and thigh-shank couplings of the intact limb both groups had similar coordination with the proximal segments leading the distal segments through most of the gait cycle. One exception to proximal leg coordination was late swing phase (80–100% of gait cycle) for the shank-foot coupling. The obvious difference between groups for the intact limb is in the pelvis-thigh coupling. For the ‘low’ knee functioning group the coupling was pelvis led (evidenced by positive CRP angle), whereas the thigh led the coupling in the ‘high’ knee functioning group.