This paper presents the model "Work Situation Operative Model" - MOST (after its Spanish acronym). It offers a comprehensive, systemic approach to analysing work stations and/or work processes, serving also as a framework for pursuing various ergonomic and occupational health and safety goals. Originally produced for a food sector company, the model has been extended and successfully applied in several industries in Colombia and Ecuador, including cement, oil, and paper industries. Based on a systemic understanding of work systems and tasks, the model not only allows different, commonly-used methods and tools for evaluating or assessing the risk of muscular-sketetal disorders to be included, but also supports occupational risk management strategies. Hence, one of its more important contributions relies on providing meaningful information that is useful for improving the work station and/or work process through design and re-design, by focusing on the interactions between all system elements.