Characterization of workplace environments has often been limited by technology or feasibility constraints. Questions about how walking surfaces affect subsequent mechanical loading in the lower extremities as a possible contributing factor in the development of lower extremity joint disease such as osteoarthritis are still unanswered. The purpose of this study was to generate data to describe the changes in external knee joint forces and moments ambulating on crushed rock aggregate surfaces on a level and transversely (side-to-side) sloped configuration. The study was designed to replicate environmental conditions experienced by railroad workers in rail yards. Ten male railroad workers were enrolled in the study and gait analysis was performed on three surface conditions (Hard Control, Small Aggregate 31.75 mm (9.53-31.75 mm), and Large Aggregate 63.5 mm (19.05-63.5 mm). and two configurations (level and 7° slant). Results included an increased knee adductor moment and medial reaction force in the upslope limb from walking on slanted surfaces. This may contribute to an increase in load in the medial compartment of the meniscus which has been associated with the progression of knee OA. The results from this study provide the most comprehensive information about human locomotion on aggregate surfaces currently available. Further analyses of soft tissue responses to changes in external loading are warranted. A comprehensive, collaborative effort to understand occupational activities and relative risk of knee OA resulting from subtle changes in lower extremity joint loads is necessary.