Does the choice of stair gait cycle affect resulting knee joint kinematics and moments?

Stair gait is a useful activity for the assessment of knee function. The aim of this study was to determine whether knee joint kinematics and moments are affected by the choice of stair gait cycle (SGC) and the step used to measure ground reaction forces (GRFs). This was investigated through motion analysis of ten non-pathological subjects as they ascended and descended a four-step staircase. The SGCs compared for ascent were, first, step 1 (measuring GRFs) to step 3 and, second, step 2 (measuring GRFs) to step 4, and vice versa for stair descent. Knee joint kinematics were not significantly influenced by the choice of SGC. For ascent, significantly larger peak adduction moments were measured for SGCs beginning on step 1 (0.30 +/- 0.08 N m/kg) than for SGCs beginning on step 2 (0.23 +/- 0.09 N m/kg). For descent, the second flexion moment peak was found to be significantly larger for SGCs ending on step 2 (1.17 +/- 0.25 N m/kg) than for SGCs ending on step 1 (0.97 +/- 0.19 N m/kg), and the first adduction moment peak was found to be significantly larger for SGCs ending on step 2 (0.28 +/- 0.15 N m/kg) than for SGCs ending on step 1 (0.21 +/- 0.18 N m/kg). This study highlights important considerations when planning stair gait measurement protocols and comparing results from studies made by other laboratories.