title: Patellofemoral pain syndrome and its association with hip, ankle, and foot function in 16- to 18-year-old high school students: a single-blind case-control study.
abstract: BACKGROUND
  An increased pronated foot posture is believed to contribute to patellofemoral pain syndrome (PFPS), but the relationship between these phenomena is still controversial. The objectives of this study were to investigate the prevalence of PFPS in high school students and to compare passive internal and external hip rotation, passive dorsiflexion, and navicular drop and drift between healthy high school students and students with PFPS.
  
  
  METHODS
  All 16- to 18-year-old students in a Danish high school were invited to join this single-blind case-control study (N = 299). All of the students received a questionnaire regarding knee pain. The main outcome measurements were prevalence of PFPS, navicular drop and drift, passive ankle dorsiflexion, passive hip rotation in the prone position, and activity level. The case group consisted of all students with PFPS. From the same population, a randomly chosen control group was formed.
  
  
  RESULTS
  The prevalence of knee pain was 25%. Of the 24 students with knee pain, 13 were diagnosed as having PFPS. This corresponds to a PFPS prevalence of 6%. Mean navicular drop and drift were higher in the PFPS group versus the control group (navicular drop: 4.2 mm [95% confidence interval (CI), 3.2-5.3 mm] versus 2.9 mm [95% CI, 2.5-3.3 mm]; and navicular drift: 2.6 mm [95% CI, 1.6-3.7 mm] versus 1.4 mm [95% CI, 0.9-2.0 mm]). Higher passive ankle dorsiflexion was also identified in the PFPS group (22.2° [95% CI, 18°-26°] versus 17.7° [95% CI, 15°-20°]).
  
  
  CONCLUSIONS
  This study demonstrated greater navicular drop, navicular drift, and dorsiflexion in high school students with PFPS compared with healthy students and highlights that foot posture is important to consider as a factor where patients with PFPS diverge from healthy individuals.
authors.affiliation: Department of Occupational and Physiotherapy, Aalborg Hospital, Surgery Research Unit, Aarhus University Hospital, Aalborg, Denmark. cmm@rn.dk
authors.forename: Carsten
authors.initials: C
authors.lastname: Mølgaard
authors.forename: Michael Skovdal
authors.initials: MS
authors.lastname: Rathleff
authors.forename: Ole
authors.initials: O
authors.lastname: Simonsen
mesh_terms: D000293:Adolescent; D018771:Arthralgia / Q000453:epidemiology / Q000503:physiopathology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000503:physiopathology*; D008297:Male; D046788:Patellofemoral Pain Syndrome / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D015995:Prevalence; D011403:Pronation / Q000502:physiology*; D012399:Rotation; D016037:Single-Blind Method