title: The relationship of foot and ankle mobility to the frontal plane projection angle in asymptomatic adults.
abstract: BACKGROUND
  The frontal plane projection angle (FPPA) is frequently used as a measure of dynamic knee valgus during functional tasks, such as the single leg squat. Increased dynamic knee valgus is observed in people with knee pathologies including patellofemoral pain and anterior cruciate injury. As the foot is the primary interface with the support surface, foot and ankle mobility may affect the FPPA. This study investigated the relationship between foot and ankle mobility and the FPPA in asymptomatic adults.
  
  
  METHODS
  Thirty healthy people (aged 18-50 years) performed 5 single leg squats. Peak FPPA and FPPA excursion were determined from digital video recordings. Foot mobility was quantified as the difference in dorsal midfoot height or midfoot width, between non-weightbearing and bilateral weightbearing positions. Ankle joint dorsiflexion range was measured as the maximum distance in centimetres between the longest toe and the wall during a knee-to-wall lunge. Linear regressions with generalised estimating equations were used to examine relationships between variables.
  
  
  RESULTS
  Higher midfoot width mobility was associated with greater peak FPPA (β 0.90, p < 0.001, odds ratio [OR] 2.5), and FPPA excursion (β 0.67, p < 0.001, OR 1.9). Lower midfoot height mobility was associated with greater peak FPPA (β 0.37, p = 0.030, OR 1.4) and FPPA excursion (β 0.30, p = 0.020, OR 1.3). Lower ankle joint dorsiflexion was also associated with greater peak FPPA (β 0.61, p = 0.008, OR 1.8) and greater FPPA excursion (β 0.56, p < 0.001, OR 1.7).
  
  
  CONCLUSIONS
  Foot and ankle mobility was significantly related to the FPPA during the single leg squat in healthy individuals. Specifically, higher midfoot width mobility, or lower ankle joint dorsiflexion range and midfoot height mobility, were associated with a greater FPPA. These foot mobility factors should be considered in the clinical management of knee-related disorders that are associated with a high FPPA.
authors.affiliation: Division of Physiotherapy, School of Health & Rehabilitation Sciences, The University of Queensland, St. Lucia Queensland, 4072 Australia.
authors.forename: Narelle
authors.identifier: 0000-0002-1952-8433
authors.initials: N
authors.lastname: Wyndow
authors.affiliation: Division of Physiotherapy, School of Health & Rehabilitation Sciences, The University of Queensland, St. Lucia Queensland, 4072 Australia.
authors.forename: Amy
authors.initials: A
authors.lastname: De Jong
authors.affiliation: Division of Physiotherapy, School of Health & Rehabilitation Sciences, The University of Queensland, St. Lucia Queensland, 4072 Australia.
authors.forename: Krystal
authors.initials: K
authors.lastname: Rial
authors.affiliation: School of Biomedical Sciences, The University of Queensland, St. Lucia Queensland, 4072 Australia.
authors.forename: Kylie
authors.initials: K
authors.lastname: Tucker
authors.affiliation: Division of Physiotherapy, School of Health & Rehabilitation Sciences, The University of Queensland, St. Lucia Queensland, 4072 Australia ; Department of Mechanical Engineering, Melbourne School of Engineering, University of Melbourne, Melbourne, VIC 3010 Australia.
authors.forename: Natalie
authors.initials: N
authors.lastname: Collins
authors.affiliation: Division of Physiotherapy, School of Health & Rehabilitation Sciences, The University of Queensland, St. Lucia Queensland, 4072 Australia.
authors.forename: Bill
authors.initials: B
authors.lastname: Vicenzino
authors.affiliation: Division of Physiotherapy, School of Health & Rehabilitation Sciences, The University of Queensland, St. Lucia Queensland, 4072 Australia.
authors.forename: Trevor
authors.initials: T
authors.lastname: Russell
authors.affiliation: Division of Physiotherapy, School of Health & Rehabilitation Sciences, The University of Queensland, St. Lucia Queensland, 4072 Australia ; School of Allied Health, College of Science, Health and Engineering, La Trobe University, Bundoora, Vic 3086 Australia.
authors.forename: Kay
authors.initials: K
authors.lastname: Crossley
mesh_terms: D000293:Adolescent; D000328:Adult; D000842:Ankle / Q000502:physiology*; D001696:Biomechanical Phenomena / Q000502:physiology; D005528:Foot / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D016014:Linear Models; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D055815:Young Adult
keywords: Ankle; Foot; Knee; Linear models
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