Study Design Retrospective cohort. Background Although persons with patellofemoral pain (PFP) often report pain with prolonged sitting, little is known about the prevalence and characteristics of sitting pain. Objectives To describe the proportion of persons with PFP who experience problems with prolonged sitting and to determine patient characteristics associated with sitting pain. Methods Four hundred fifty-eight participants with a diagnosis of PFP from 4 separate studies were included. Item 8 of the Anterior Knee Pain Scale was used to define the presence of problems with prolonged sitting with knee flexion, based on 3 categories: (1) "no difficulty," (2) "pain after exercise," or (3) "problems with prolonged sitting." Differences in demographic and clinical variables between categories were evaluated using Kruskal-Wallis tests (P<.05). Results Two hundred forty-nine (54.4% of the study sample) participants reported problems with prolonged sitting, and 121 (26.4%) reported sitting pain after exercise. Compared to those with no difficulty sitting (n = 88), participants classified as having problems with prolonged sitting were significantly younger (P = .038), more likely to be female (P = .033), had a lower body mass index (P = .027), reported higher pain severity (P<.001) and lower Anterior Knee Pain Scale scores (P<.001), and more frequently reported problems with squatting (P<.001). Conclusion Problems with prolonged sitting are evident in more than half of persons with PFP. Findings highlight the need to identify and adequately manage PFP associated with prolonged sitting. Further research should explore mechanisms of sitting pain and evaluate targeted interventions to reduce PFP with prolonged sitting. Level of Evidence Symptom prevalence study, level 2b. J Orthop Sports Phys Ther 2016;46(8):658-663. Epub 3 Jul 2016. doi:10.2519/jospt.2016.6470.