Background: Accidents involving interprovincial buses are a significant road safety issue, with mechanical failures in brakes and brake shoes being the most common causes. Due to its complexity, the development process of these maintenance activities is not well-studied. This potentially exposes mechanics to system factors that increase the risk of musculoskeletal disorders (MSD). Aim: The study used a systems approach to investigate the risk of musculoskeletal disorder (MSD) in mechanics workers who change brake shoes on interprovincial buses. Materials and Methods: A mixed-method study was conducted. The research tools included semi-structured interviews and structured field observations. Information was categorised using a systems model based on Smith and Carayon and organised through Hierarchical Task Analysis (HTA). The REBA method was applied to the sequence of activities, and the MAC tool was used to assess the risk of MSD in manual handling. Result: Barriers and facilitators were identified, such as inadequate tools and improvised tool design without validation, the lack of space to make shoe changes, and empirical knowledge about the techniques without technical procedures. Postural overload (REBA > 8) was also observed during more than 70% of the activities, and manual handling of loads with risk (MAC > 16) when handling pneumatic guns. Conclusions: Mechanical workers are exposed to work system risk factors that contribute to a high incidence of MSD when performing shoe-changing tasks. The study proposed a low-fidelity prototype articulated knee brace to represent the reduction of knee effort to facilitate correct positioning during brake shoe change.