This systematic review critically evaluates the quantification of soft tissue artifact (STA) in lower limb human motion analysis. It has a specific focus on assessing the quality of previous studies and comparing quantitative results. A specific search strategy identified 20 published articles or abstracts that fulfilled the selection criteria. The quality of the articles was evaluated using a customised critical appraisal tool. Data extraction tools were used to identify key aspects reported in the articles. Most studies had small sample sizes of mostly young, slim participants. Eleven of the reviewed articles used physically invasive techniques to assess STA. STA was found to reach magnitudes of greater than 30 mm on the thigh segment, and up to 15 mm on the tibia. The range of soft tissue artifact reached greater than 25 mm in some cases when comparing the results of reviewed studies.