Evidence Based Orthopaedics: Prognostic Studies addresses the use of prognostic studies in evidence-based medicine. Prognostic studies can be used to better understand the natural history of a disease or identify subgroups of patients and can help guide clinical decision making. This module examines a case study as an example to outline the use of prognostic studies as evidence in clinical care decisions. It addresses the types of primary studies used to assess prognosis, evaluation of prognostic studies as evidence, and the how to compare and assess the validity of the studies.