Research considerations based on the evidence for the incidence and prevalence of patellofemoral pain syndrome

I commend Oakes and colleagues for taking the time to critically review previously published articles on the incidence and prevalence of patellofemoral pain syndrome (PFPS). I agree that there is a lack of recent epidemiologic data on the occurrence of PFPS and among the studies that have been published there is lack of consistency in methodologies. There are a few conclusions made by the authors that I would like to expand upon. First, the authors conclude that future research should investigate the incidence and prevalence of PFPS in younger athletic populations. I agree with this statement but I also want to iterate the challenges with collecting epidemiologic data on PFPS in younger populations. One difficulty that researchers will encounter is that PFPS develops over time and may require a lengthy follow-up period, especially in a younger population in which the physical activity demands may be lower than a collegiate aged population. Additionally, PFPS does not have a specific injury definition, making it even more difficult to track diagnoses of this injury. Many studies have been performed in military populations most likely due to the closed medical system (all medical records go into a single medical record database) and the requirement for high levels of physical activity in this population. As mentioned by the authors, better methodologies and questionnaires need to be developed for the investigation of incidence and prevalence of PFPS. Once this occurs, I believe we will see an increase in the number of successful epidemiological studies on PFPS in younger athletic populations. Additionally, the authors note the lack of evidence for the incidence and prevalence of PFPS in both males and females. It is commonly cited that females have a higher occurrence of PFPS compared to males, but this statement lacks scientific support. Many of the studies performed in military populations have utilized a predominantly male population to describe the incidence of PFPS. A recent epidemiologic investigation not included in this review, provides scientific evidence for the increased predisposition of females to PFPS in the military. Although this recent investigation addresses one of the gaps in the literature identified by the authors, more research is needed to understand if these results can be generalized to a younger athletic population. Based on this review and the lack of recent epidemiologic evidence for PFPS, I encourage researchers in sports medicine to perform additional prospective investigations so that we may better understand the risk factors for PFPS and the incidence of this condition in various populations. Risk factors for PFPS cannot be identified from a retrospective study (Taunton et al.) and should be identified through prospective cohort investigations, such as the investigation by Witvrouw et al. Furthermore, there is a need for researchers and clinicians to better understand why females are reported to develop this condition more often than males. With increased research on the epidemiology of PFPS, we will gain a better understanding of the risk factors for PFPS, helping to explain the increased predisposition of females to this condition.