What is the Foot and Ankle Disability (FADI)?
The Foot and Ankle Disability Index (FADI) is a self-administered patient-reported outcome survey that measures functional limitations related to foot and ankle conditions. It has a total of 26 items distributed among two subscales: an Activity subscale (22 items) and a Pain subscale (4 items). An additional 8-item FADI Sports subscale can be used as well to assess more difficult tasks that are essential to sports (1).
The FADI was first described by Dr. RobRoy L. Martin and colleagues in 1999 via the Journal of Orthopaedic Sports Physical Therapy (2). Of note, Dr. Martin and colleagues also developed the Foot and Ankle Ability Measure (FAAM) in 2005, which is a commonly used newer version of the FADI (3). The FAAM is almost identical to the FADI with the exception of 5 items that are excluded from the FAAM: the 4 items of the Pain subscale and a sleeping item from the Activity subscale. The FAAM Sports subscale is identical to the FADI Sports subscale.
Structure and Scoring
The FADI is composed of 2 subscales with a total of 26 scored items: the Activity subscale (22 items) and the Pain subscale (4 items). In the FADI Activity subscale, each item describes the degree of inability to perform certain physical activities, such as standing or walking on an even surface, and is rated on a 5-point Likert scale from “None at all” to “Unable to do”. In the FADI Pain subscale, each item describes the degree of pain experienced according to four states of activity (general, at rest, normal activity, and first thing in the morning) and is also rated on a 5-point Likert scale from “No pain” to “Unbearable”. Both FADI Activity and Pain subscales also include a “Not Applicable” option for each item separate from the Likert scale.
The FADI is scored out of 104, with a score of 0 indicating maximum disability and a score of 104 indicating no disability. The total FADI score corresponds to the sum of Activity and Pain subscale scores (maximum score of 88 for Activity and 16 for Pain). For both subscales, the lowest degree of disability or pain on the Likert scale of each item corresponds to a score of 4 (i.e. “None at all” for Activity, “No pain” for Pain). This score incrementally decreases by 1 along the Likert scale, with a score of 0 corresponding to the highest degree of disability or pain (i.e. “Unable to do” for Activity, “Unbearable” for Pain). For every item in either subscale where the “Not Applicable” option is selected, the total FADI maximum score decreases by 4 (e.g. selecting one “Not Applicable” item produces a total maximum score of 100 instead of 104).
Strengths
The FADI and the FADI Sports subscale have both been shown to be highly reliable (1), valid (1, 4), and responsive (6). Hale and Hertel (1) found significantly lower scores for the affected limbs of chronic ankle instability patients compared to the contralateral limb as well as no differences between limbs in healthy subjects. They also calculated excellent intraclass correlation coefficients (0.84 to 0.93). Pugia et al. (5) reported moderate to good correlations between FADI and other validated scales (0.50 to 0.79). Eechaute et al. (6) demonstrated significant increases in effect size after rehabilitation.
Considerations
The FADI can be perceived as lengthy given its range of 26 to 34 items (if the Sports subscale is to be included). Because it is patient-administered, it relies on patient understanding of the tool. Most studies reporting on FADI as a measuring tool have been conducted exclusively in patients with chronic ankle instability, limiting the generalizability to other conditions. At the time of publishing this article, no minimum clinically important difference (MCID) has been calculated for FADI. Of note, FAAM as a tool has been studied in other conditions and has a reported MCID in the literature.
Overall, the FADI is a reliable, valid, responsive, and free patient-reported outcome measure. When evaluating the use of this tool, it is important to keep in mind that a majority of the studies have been conducted on patients with chronic ankle instability which may limit its use in other foot conditions.
License
The FADI is free to use and does not have any licensing requirements.
References
- Hale SA, Hertel J. Reliability and Sensitivity of the Foot and Ankle Disability Index in Subjects With Chronic Ankle Instability. J Athl Train. 2005 Mar;40(1):35-40. PMID: 15902322; PMCID: PMC1088343.
- Martin RL, Burdett RG, Irrgang JJ. Development of the foot and ankle disability index (FADI). J Orthop Sports Phys Ther. 1999;29(1):A32-3.
- Martin RL, Irrgang JJ, Burdett RG, Conti SF, Swearingen JM. Evidence of validity for the Foot and Ankle Ability Measure (FAAM). Foot & ankle international. 2005 Nov;26(11):968-83.
- Krishnan C, Williams GN, Delaney F, Hicks M, Iler M, Harms S. Antagonist muscle activity during maximal isometric knee strength testing. J Orthop Sports Phys Ther. 2007;37(1):A72-3.
- Pugia ML, Middel CJ, Seward SW, Pollock JL, Hall RC, Lowe L, Mahony L, Henderson NE. Comparison of acute swelling and function in subjects with lateral ankle injury. J Orthop Sports Phys Ther. 2001 Jul;31(7):384-8. doi: 10.2519/jospt.2001.31.7.384. PMID: 11451309.
- Eechaute C, Vaes P, Van Aerschot L, Asman S, Duquet W. The clinimetric qualities of patient-assessed instruments for measuring chronic ankle instability: a systematic review. BMC Musculoskelet Disord. 2007 Jan 18;8:6. doi: 10.1186/1471-2474-8-6. PMID: 17233912; PMCID: PMC1797175.
