title: A digital photographic measurement method for quantifying foot posture: validity, reliability, and descriptive data.
abstract: BACKGROUND
  Although abnormal foot posture long has been associated with lower extremity injury risk, the evidence is equivocal. Poor intertester reliability of traditional foot measures might contribute to the inconsistency.
  
  
  OBJECTIVE
  To investigate the validity and reliability of a digital photographic measurement method (DPMM) technology, the reliability of DPMM-quantified foot measures, and the concurrent validity of the DPMM with clinical-measurement methods (CMMs) and to report descriptive data for DPMM measures with moderate to high intratester and intertester reliability.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Biomechanics research laboratory.
  
  
  METHODS
  A total of 159 people participated in 3 groups. Twenty-eight people (11 men, 17 women; age  =  25 ± 5 years, height  =  1.71 ± 0.10 m, mass  =  77.6 ± 17.3 kg) were recruited for investigation of intratester and intertester reliability of the DPMM technology; 20 (10 men, 10 women; age  =  24 ± 2 years, height  =  1.71 ± 0.09 m, mass  =  76 ± 16 kg) for investigation of DPMM and CMM reliability and concurrent validity; and 111 (42 men, 69 women; age  =  22.8 ± 4.7 years, height  =  168.5 ± 10.4 cm, mass  =  69.8 ± 13.3 kg) for development of a descriptive data set of the DPMM foot measurements with moderate to high intratester and intertester reliabilities.
  
  
  METHODS
  The dimensions of 10 model rectangles and the 28 participants' feet were measured, and DPMM foot posture was measured in the 111 participants. Two clinicians assessed the DPMM and CMM foot measures of the 20 participants.
  
  
  METHODS
  Validity and reliability were evaluated using mean absolute and percentage errors and intraclass correlation coefficients. Descriptive data were computed from the DPMM foot posture measures.
  
  
  RESULTS
  The DPMM technology intratester and intertester reliability intraclass correlation coefficients were 1.0 for each tester and variable. Mean absolute errors were equal to or less than 0.2 mm for the bottom and right-side variables and 0.1° for the calculated angle variable. Mean percentage errors between the DPMM and criterion reference values were equal to or less than 0.4%. Intratester and intertester reliabilities of DPMM-computed structural measures of arch and navicular indices were moderate to high (>0.78), and concurrent validity was moderate to strong.
  
  
  CONCLUSIONS
  The DPMM is a valid and reliable clinical and research tool for quantifying foot structure. The DPMM and the descriptive data might be used to define groups in future studies in which the relationship between foot posture and function or injury risk is investigated.
authors.affiliation: Department of Human Movement Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201-0413, USA. cobbsc@uwm.edu
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Cobb
authors.forename: C Roger
authors.initials: CR
authors.lastname: James
authors.forename: Matthew
authors.initials: M
authors.lastname: Hjertstedt
authors.forename: James
authors.initials: J
authors.lastname: Kruk
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005528:Foot / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D035002:Lower Extremity / Q000293:injuries; D008297:Male; D009068:Movement; D010781:Photography / Q000379:methods*; D011187:Posture / Q000502:physiology; D011403:Pronation; D012016:Reference Values; D015203:Reproducibility of Results; D012307:Risk Factors; D055815:Young Adult