Musculoskeletal models estimates can be heavily affected by the soft tissue artefact (STA) when input positional data are obtained using stereophotogrammetry. In this study, we assessed the sensitivity to the STA of three open-source musculoskeletal models and relevant tools, implemented in OpenSim. To this purpose, a baseline dataset of marker trajectories was created using point kinematics for each model from experimental data of one healthy volunteer’s gait. Five hundred STA realizations were then statistically generated using a marker-dependent model of the pelvis and lower limb artefact and added to the baseline data. The STA's impact on the musculoskeletal model estimates of an inverse dynamics pipeline (joint angles, joint moments, and muscle and joint contact forces) was finally quantified using a Monte Carlo analysis.