Lower limb biomechanics of walking on slanted and level railroad ballast

Work is an essential part of human existence providing sources of income and economic stimulation to society. Perhaps more importantly, it can also provide structure and meaning to an individual's life. Some workplace environments can pose threats to human health and reduce overall quality of life as a result of injury. Knee osteoarthritis (OA) can cause severe functional limitations and reduce quality of life. Some data suggest that more than 70% of total knee and hip arthroplasty can be contributed to OA. Little is known about the relationship between mechanical loading of the knee and subsequent development of knee OA. Characterization of workplace environments has often been limited by technology or feasibility constraints. The purpose of this study was to develop a technique capable of performing an analysis of lower limb biomechanics for walking on irregular surfaces, specifically crushed rock aggregate (ballast) to better understand lower extremity biomechanics. The relationship between mechanical loads and subsequent development of knee OA is unclear. A goal was to better understand mechanical loading during ambulation on aggregate surfaces, specifically of the knee, to quantify exposures to be used in epidemiological studies to help identify causation. Custom walkways and a force plate isolation fixture were developed, making this study feasible. The most significant findings for this study were related to medial/lateral joint forces and abductor/adductor moments produced at the knee because of aggregate surface configurations (side-to-side slope). The upslope limb responded differently than the downslope limb to a sloped configuration in the transverse plane (side-to-side). These data constitute the most comprehensive dataset currently available to understand gait on aggregate surfaces. Data collected from this study can be used in future epidemiological studies to develop more complete models to predict the likelihood of knee osteoarthritis from exposure to walking on aggregate. Such studies should evaluate the prevalence and incidence rates of knee OA in railroad workers and compare them to rates in a control population. Control for potential confounding factors such as age and occupation will need special attention. Additional information about duration and intensity of exposure will be important variables necessary to better understand causes of knee OA from occupational exposures of walking on irregular terrain, specifically aggregates.