title: Are there three main subgroups within the patellofemoral pain population? A detailed characterisation study of 127 patients to help develop targeted intervention (TIPPs).
abstract: BACKGROUND
  Current multimodal approaches for the management of non-specific patellofemoral pain are not optimal, however, targeted intervention for subgroups could improve patient outcomes. This study explores whether subgrouping of non-specific patellofemoral pain patients, using a series of low cost simple clinical tests, is possible.
  
  
  METHODS
  The exclusivity and clinical importance of potential subgroups was assessed by applying à priori test thresholds (1 SD) from seven clinical tests in a sample of adult patients with non-specific patellofemoral pain. Hierarchical clustering and latent profile analysis, were used to gain additional insights into subgroups using data from the same clinical tests.
  
  
  RESULTS
  130 participants were recruited, 127 had complete data: 84 (66%) female, mean age 26 years (SD 5.7) and mean body mass index 25.4 (SD 5.83), median (IQR) time between onset of pain and assessment was 24 (7-60) months. Potential subgroups defined by the à priori test thresholds were not mutually exclusive and patients frequently fell into multiple subgroups. Using hierarchical clustering and latent profile analysis three subgroups were identified using 6 of the 7 clinical tests. These subgroups were given the following nomenclature: (1) 'strong', (2) 'weak and tighter' and (3) 'weak and pronated foot'.
  
  
  CONCLUSIONS
  We conclude that three subgroups of patellofemoral patients may exist based on the results of six clinical tests which are feasible to perform in routine clinical practice. Further research is needed to validate these findings in other data sets and, if supported by external validation, to see if targeted interventions for these subgroups improve patient outcomes.
authors.affiliation: University of Central Lancashire, Preston, Lancashire, UK.
authors.forename: James
authors.initials: J
authors.lastname: Selfe
authors.affiliation: University of Central Lancashire, Preston, Lancashire, UK.
authors.forename: Jessie
authors.initials: J
authors.lastname: Janssen
authors.affiliation: Institute for Inflammation and Repair, Centre for Musculoskeletal Research, University of Manchester, Manchester, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Callaghan
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
authors.forename: Erik
authors.initials: E
authors.lastname: Witvrouw
authors.affiliation: University of Central Lancashire, Preston, Lancashire, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Sutton
authors.affiliation: University of Central Lancashire, Preston, Lancashire, UK.
authors.forename: Jim
authors.initials: J
authors.lastname: Richards
authors.affiliation: Faculty of Health Sciences, University of Southampton, Southampton, UK.
authors.forename: Maria
authors.initials: M
authors.lastname: Stokes
authors.affiliation: Teesside University, Middlesbrough, UK.
authors.forename: Denis
authors.initials: D
authors.lastname: Martin
authors.affiliation: Teesside University, Middlesbrough, UK.
authors.forename: John
authors.initials: J
authors.lastname: Dixon
authors.affiliation: University of Central Lancashire, Preston, Lancashire, UK.
authors.forename: Russell
authors.initials: R
authors.lastname: Hogarth
authors.affiliation: Brunel University London, Uxbridge, UK.
authors.forename: Vasilios
authors.initials: V
authors.lastname: Baltzopoulos
authors.affiliation: Department of Physiotherapy, Harrogate & District NHS Foundation Trust, Harrogate District Hospital, Harrogate, North Yorkshire, UK.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ritchie
authors.affiliation: University of Oxford, Nuffield Orthopaedic Centre, Oxford, UK.
authors.forename: Nigel
authors.initials: N
authors.lastname: Arden
authors.affiliation: University of Central Lancashire, Preston, Lancashire, UK.
authors.forename: Paola
authors.initials: P
authors.lastname: Dey
mesh_terms: D000328:Adult; D016000:Cluster Analysis; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D053580:Muscle Strength; D010147:Pain Measurement; D046788:Patellofemoral Pain Syndrome / Q000145:classification* / Q000175:diagnosis* / Q000628:therapy; D011403:Pronation; D016059:Range of Motion, Articular; D055815:Young Adult
keywords: Knee; Physiotherapy
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