title: Altering foot progression angle in people with medial knee osteoarthritis: the effects of varying toe-in and toe-out angles are mediated by pain and malalignment.
abstract: OBJECTIVE
  To evaluate if altering the foot progression angle (FPA) by varying magnitudes during gait alters the external knee adduction moment (KAM), knee flexion moment (KFM), knee extension moment (KEM) and/or symptoms in people with medial knee osteoarthritis (OA). Potential influence of pain and knee malalignment on load-modifying effects of FPA was investigated.
  
  
  METHODS
  Participants (n = 22) underwent 3-dimensional gait analysis to measure KAM peaks, KAM impulse, KFM and KEM peaks. Following natural gait, five altered FPA conditions were performed in random order (10° toe-in, 0° FPA, 10° toe-out, 20° toe-out and 30° toe-out). A projection screen displayed their real-time FPA. Pain/discomfort at knees and feet/ankles were evaluated for each condition. Linear mixed models were used for statistical analysis.
  
  
  RESULTS
  Toe-in reduced the early stance peak KAM and KEM but increased the KAM impulse, late stance peak and KFM. Toe-out reduced the KAM impulse, late stance peak and KFM (P < 0.001) but increased the early stance peak KAM and KEM. All effects were greater in participants with more varus knees. Pain significantly mediated the effect of altered FPA on the KAM impulse and late stance peak. In more painful individuals, toe-in was predicted to reduce the KAM impulse and late stance peak, and increase them for toe-out gait. There were no immediate symptomatic changes.
  
  
  CONCLUSIONS
  Effects of altered FPA vary across all medial knee load parameters and it is difficult to determine an optimal direction of FPA change. Future studies should consider Western Ontario McMaster Universities OA Index (WOMAC) pain to judge the likely effects of altered FPA.
authors: Centre for Health, Exercise and Sports Medicine, Department of Physiotherapy, School of Health Sciences, University of Melbourne, Australia. milena.simic@sydney.edu.au
authors: M
authors: M
authors: Simic
authors: T V
authors: TV
authors: Wrigley
authors: R S
authors: RS
authors: Hinman
authors: M A
authors: MA
authors: Hunt
authors: K L
authors: KL
authors: Bennell
mesh_terms: D000368:Aged; D000843:Ankle Joint / Q000502:physiology; D018771:Arthralgia / Q000503:physiopathology* / Q000534:rehabilitation; D001696:Biomechanical Phenomena; D005260:Female; D033023:Foot Joints / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology* / Q000534:rehabilitation; D026741:Physical Therapy Modalities; D014034:Toes / Q000502:physiology; D016138:Walking; D016474:Weight-Bearing / Q000502:physiology
keywords: Adduction moment; Foot progression angle; Gait modification; Knee; Load; Osteoarthritis; Toe-in; Toe-out