Foot Posture Index (FP1-6)

Original Editor - Rachael Lowe

Top Contributors - Rachael Lowe, Mariam Hashem, Evan Thomas and Amanda Ager  

Objective

The FPI-6 is a novel method of rating foot posture using set criteria and a simple scale. It is a clinical tool used to quantify the degree to which a foot is pronated, neutral or supinated. It is a measure of standing foot posture and so is not a replacement for gait assessment where time and facilities exist. It is however a more valid approach than many of the static weightbearing and non-weightbearing goniometric measures currently used in clinic.

Intended Population

The FPI has been used in a variety of clinical and research settings. The applications of the FPI include studies of biomechanical risk factors for neuropathic ulceration in diabetes , identifying foot type as a basis for screening subjects as inclusion or exclusion criteria in clinical research, investigating the relationship between foot types and risk factors for sports and training injuries, investigating whether foot posture is associated with falls in older people and as a means of assessing age-related differences in foot structure.[1]

Method of Use

The patient should stand in their relaxed stance position with double limb support. The patient should be instructed to stand still, with their arms by the side and looking straight ahead. It may be helpful to ask the patient to take several steps, marching on the spot, prior to settling into a comfortable stance position. During the assessment, it is important to ensure that the patient does not swivel to try to see what is happening for themself, as this will significantly affect the foot posture. The patient will need to stand still for approximately two minutes in total in order for the assessment to be conducted. The assessor needs to be able to move around the patient during the assessment and to have uninterrupted access to the posterior aspect of the leg and foot. If an observation cannot be made (e.g. because of soft tissue swelling) simply miss it out and indicate on the datasheet that the item was not scored.  If there is genuine doubt about how high or low to score an item always use the more conservative score.

-2 -1 0 +1 +2
Talar head palpation Talar head palpable on lateral side/but not on medial side Talar head palpable on lateral/slightly palpable on medial side Talar head equally palpable on lateral and medial side Talar head slightly palpable on lateral side/palpable on medial side Talar head not palpable on lateral side/but palpable on medial side

Supra and infra lateral malleoli curvature (viewed from behind)

Curve below the malleolus either straight or convex Curve below the malleolus concave, but flatter/more than the curve above the malleolus Both infra and supra malleolar curves roughly equal Curve below the malleolus more concave than curve above malleolus Curve below the malleolus markedly more concave than curve above malleolus
Calcaneal frontal plane position (viewed from behind) More than an estimated 5o inverted (varus) Between vertical and an estimated 5o inverted (varus) Vertical Between vertical and an estimated 5o everted (valgus) More than an estimated 5o everted (valgus)
Prominence in region of TNJ (viewed at an angle from inside Area of TNJ markedly concave Area of TNJ slightly, but definitely concave Area of TNJ flat Area of TNJ bulging slightly Area of TNJ bulging markedly
Congruence of medial longitudinal arch (viewed from inside) Arch high and acutely angled towards the posterior end of the medial arch Arch moderately high and slightly acute posteriorly Arch height normal and concentrically curved Arch lowered with some flattening in the central position Arch very low with severe flattening in the central portion - arch making ground contact
Abduction/adduction of forefoot on rearfoot (view from behind) No lateral toes visible. Medial toes clearly visible Medial toes clearly more visible than lateral Medial and lateral toes equally visible Lateral toes clearly more visible than medial No medial toes visible. Lateral toes clearly visible.

Features commensurate with an approximately neutral foot posture are graded as zero, while pronated postures are given a positive value, and supinated features as negative value. when the scores are combined, the aggregate value gives an estimate of the overall foot posture. high positive aggregate values indicate a pronated posture, significantly negative aggregate values indicate a supinated overall foot posture, while for a neutral foot the final FPI aggregate score should lie somewhere around zero[2].

Evidence

Menz H (1998). Alternative techniques for the clinical assessment of foot posture. JAPMA; 88(3):119-129

Evans A et al (2003). Reliability of the foot posture index and traditional measures of foot position. JAPMA; 93(3): 203-213

Reliability

Morrison & Ferrari studied the inter-rater reliability of the FPI-6 in the assessment of the pediatric foot, and there was inter-rater agreement when the actual score was compared using a weighed Kappa test (Kw = 0.88). The study concluded that the FPI-6 is a quick, simple and reliable clinical tool which has demonstrated good inter-rater reliability when used in the assessment of the pediatric foot[3].

Validity

The FPI-6 has been subjected to evaluation against the Rasch statistical model. This analysis confirms the construct validity of the six-item instrument and the linearity of the metric output[4]. (PSI=0.88)

Resources

References

  1. Redmond, A. C., Crane, Y. Z., & Menz, H. B. (2008). Normative values for the Foot Posture Index, 9, 1–9. https://doi.org/10.1186/1757-1146-1-6
  2. Guide, U. (2005). Easy quantification of standing foot posture Six item version USER GUIDE AND MANUAL, (August), 1–19.
  3. Stewart C Morrison and Jill Ferrari. Inter-rater reliability of the Foot Posture Index (FPI-6) in the assessment of the paediatric foot. Journal of Foot and Ankle Research, 2009, 2:26
  4. Keenan, AM, Redmond, A.C, Horton, M, Conaghan, PG, Tennant, A. The Foot Posture Index: Rasch analysis of a novel, foot specific outcome measure. Rheumatology 2006 45:1
  5. Anthony C. Redmond, A.C., Crosbie, J., & Ouvrier, R.A. (2006). Development and validation of a novel rating system for scoring standing foot posture: The Foot Posture Index. Clinical Biomechanics 21: 89–98.
  6. Keenan, A.M., et al. (2006). The Foot Posture Index: Rasch Analysis of a Novel, Foot-Specific Outcome Measure. Presented in part to Health Outcomes 2005: Making a Difference, August 17–18, 2005, Canberra, Australia, and the British Society for Rheumatology, May 17–18, 2006, Glasgow, Scotland. Doi : [/doi.org/10.1016/j.apmr.2006.10.005 https://doi.org/10.1016/j.apmr.2006.10.005]