Knee adduction moment peak and impulse do not change during the first six months of walking with a prosthesis

Background: Individuals with unilateral lower limb loss are at increased risk for developing knee osteoarthritis in their contralateral limb. The mechanisms underlying this phenomenon are unknown, but large or unusual loads on the limb are thought to contribute to osteoarthritis development. Yet, to our knowledge, there have been no longitudinal assessments of knee joint kinetics to assist with identifying the origin or progression of such loads. Research question: This study aimed to examine knee joint kinetics of individuals with lower limb loss as a function of time from independent ambulation. Methods: Eight male Service Members with unilateral lower limb loss (3 transfemoral/5 transtibial) completed gait analyses, walking at self-selected speed and cadence, at 0, 2, and 6 months following initial independent ambulation. Results: Although there was a significant time effect on stride length (p = 0.047), there were no pairwise differences (all p ≥ 0.152). Additionally, there was not a significant effect of time on the peak (p = 0.666), loading rate (p = 0.336), or impulse (p = 0.992) of knee adduction moment (KAM), peak knee flexion moment (KFM) (p = 0.128), or the peak (p = 0.485) or loading rate (p = 0.130) of vertical ground reaction force (VGRF). Significance: The results of the current study demonstrate that major features of knee joint loading do not change over the first 6 months of independently walking with a prosthesis. The magnitude of these loads are similar to loads observed in individuals with lower limb loss further from injury/initial ambulation, but the present results do not imply that no changes occur after 6 months.