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AOFAS Ankle-Hindfoot Calculator

AOFAS Ankle-Hindfoot Scale

The AOFAS Ankle-Hindfoot Scale is a 100-point clinician-administered rating combining 40 points for pain, 50 for function across seven items and 10 for alignment — and although it remains the most-reported outcome in the foot and ankle literature, the society that published it withdrew its endorsement in 2011 because it was never validated.

No licence required9 items~8 min0–100, higher is better

Pain (40 points)

Record the patient’s usual level of ankle and hindfoot pain.

1Pain

Function (50 points)

Seven items. The first three are reported by the patient; gait, motion and stability are measured or observed by the examiner.

2Activity limitations and support requirement
3Maximum walking distance, in blocks

A city block is roughly 100 metres. The item is one of the reasons the scale translates poorly outside North America.

4Walking surfaces
5Gait abnormality
6Sagittal motion — dorsiflexion plus plantarflexion

Measure the total sagittal arc at the ankle with a goniometer.

7Hindfoot motion — inversion plus eversion

Expressed as a percentage of the motion in the unaffected hindfoot.

8Ankle-hindfoot stability — anteroposterior and varus-valgus

All-or-nothing: there is no intermediate response for a mildly lax ankle.

Alignment (10 points)

Assess the standing alignment of the hindfoot and whether the foot is plantigrade.

9Alignment

What the AOFAS Ankle-Hindfoot score means

AOFAS Ankle-Hindfoot scores run from 0 to 100, where a higher score is better. The bands below are conventional reporting categories, not diagnostic cut-offs.

  • Poor0–69.9

    These four grades are a convention that grew up in the literature; the authors defined no severity categories, and no minimal clinically important difference has been established for this scale.

  • Fair70–79.9
  • Good80–89.9
  • Excellent90–100

How the score is calculated

Stated in full so the calculation can be independently checked, and reproduced by hand if needed.

The nine items are scored independently and added to a maximum of 100. Pain contributes 40 points (none 40, mild and occasional 30, moderate and daily 20, severe and almost always present 0). Function contributes 50 points across seven items: activity limitation and support requirement 0–10, maximum walking distance in blocks 0–5, walking surfaces 0–5, gait abnormality 0–8, sagittal ankle motion 0–8, hindfoot motion 0–6, and ankle-hindfoot stability 0 or 8. Alignment contributes 10 points (good 10, fair 5, poor 0). A higher total is better. Four of the function items (gait, sagittal motion, hindfoot motion and stability) and the alignment item require a physical examination, so 40 of the 100 points cannot be obtained from the patient alone. Grades of excellent, good, fair and poor at 90, 80 and 70 are a convention that arose in the literature rather than part of the original publication, and no minimal clinically important difference has been established.

Missing data

There is no imputation rule. Every item must be assessed for the total to be valid, and a total reported with items missing is not comparable with a complete score or with published series. Unanswered items contribute zero in the calculator above, which understates the score — a partial figure is shown only so the entry can be checked, and must not be graded.

Instrument profile

Developer
Harold B. Kitaoka, Ian J. Alexander, Robert S. Adelaar, James A. Nunley, Mark S. Myerson and Michael Sanders
Institution
American Orthopaedic Foot and Ankle Society, United States
First published
1994
Custodian
American Orthopaedic Foot and Ankle Society, which formally withdrew its endorsement of its clinical rating systems in 2011
Items
9
Response format
Nine fixed-choice items, of which five are examination findings
Score range
0 to 100
Direction
Higher score = better
Recall period
Current status at the time of examination
Completion time
About 8 minutes
Age range
Adults
Regions
Foot & Ankle
Conditions
Ankle osteoarthritis, Ankle fracture, Chronic ankle instability, Osteochondral lesion of the talus, Hindfoot arthritis, Posterior tibial tendon dysfunction
Procedures
Ankle arthrodesis, Total ankle replacement, Ankle fracture fixation, Lateral ligament reconstruction, Subtalar arthrodesis
Languages
English, Brazilian Portuguese, Spanish, Turkish, Chinese, Italian, German
Observer agreement
Never established by the developers. Later independent work reports reliability only for particular translated versions, not for the scale as originally published.
Validity
The 2003 correlation study against the SF-36 provided partial construct validity, but the scale was published without the item-generation, weighting or validation work that current standards require — the point weightings were assigned by expert consensus rather than derived.
Reliability
Widely used to report change after ankle surgery, but with no established minimal clinically important difference a change of a given number of points cannot be called meaningful.
Ceiling effect
Marked. A patient with a fused but painless, well-aligned, plantigrade foot can score 80 or more despite having essentially no ankle motion, because the motion items carry only 14 of the 100 points.
Floor effect
Uncommon.

Normative values

Reference values from published cohorts, for comparison against the score you calculated.

PopulationAgeMeanSD
Healthy ankles—At or close to 100, with a pronounced ceiling effect—

When to use the AOFAS Ankle-Hindfoot

Well suited to

  • Reading and comparing the existing foot and ankle literature, the great majority of which reports AOFAS scores.
  • Continuing a long-running series or registry that has collected the scale from the start, where switching measures would break the comparison.

Limitations and poor fits

  • Choosing a primary outcome measure for a new study or service — the AOFAS itself withdrew its endorsement in 2011, and validated patient-reported alternatives exist: the FAAM, the FAOS and the PROMIS physical function measures.
  • Postal, telephone or electronic follow-up: 40 of the 100 points require a physical examination.
  • Judging whether an individual patient has improved meaningfully, since no minimal clinically important difference has been established.
  • Comparing series across countries without checking the walking-distance item, which is expressed in city blocks and is interpreted inconsistently outside North America.
  • Assessing the midfoot, hallux or lesser toes, which have their own scales in the same 1994 publication.

AOFAS Ankle-Hindfoot compared with other instruments

Instruments measuring a related construct, with the practical difference between them.

InstrumentItemsRangeWhat it adds
FAAM290–100The FAAM is a 29-item patient-reported questionnaire for musculoskeletal disorders of the leg, foot and ankle that produces two separate subscale scores — Activities of Daily Living from 21 items and Sports from 8 items — each expressed from 0% (unable to perform the listed activities) to 100% (no limitation).
FAOS420–100The FAOS is a 42-item patient-reported questionnaire adapted from the KOOS that scores foot and ankle problems as five separate subscales — Symptoms, Pain, Activities of Daily Living, Sport and Recreation, and Quality of Life — each from 0 (extreme problems) to 100 (no problems).
LEFS200–80The LEFS is a 20-item patient-reported questionnaire that measures difficulty with everyday lower limb activities on a single 0 to 80 scale, where 80 indicates no difficulty and a change of 9 points is the smallest difference patients reliably notice.
Weber31–3The Danis-Weber classification sorts ankle fractures into three types by the level of the fibular fracture relative to the tibiotalar joint line — type A below the syndesmosis, type B at it, and type C above it — because the height of the fibular fracture predicts how much of the syndesmosis is torn.
Sanders31–4The Sanders classification grades displaced intra-articular calcaneal fractures into four types by the number of posterior facet fragments seen on the widest coronal CT image — type I non-displaced, type II two-part, type III three-part and type IV four-part or comminuted — and the type number predicts the outcome of internal fixation.

Copyright and permitted use

Published openly because it is the question every clinician and researcher asks before using an instrument, and almost nobody answers it.

No licence required

A clinician-administered rating method published in full in the peer-reviewed literature in 1994, reproduced throughout the foot and ankle literature with no licensing programme. No licence is required. Note that the publishing society has since withdrawn its endorsement of the scale — a scientific caveat rather than a legal restriction, but one that should carry more weight than the licence status when choosing an outcome measure.

References

  1. Kitaoka HB, Alexander IJ, Adelaar RS, Nunley JA, Myerson MS, Sanders M. Clinical rating systems for the ankle-hindfoot, midfoot, hallux, and lesser toes. Foot and Ankle International. 1994.
  2. Pinsker E, Daniels TR. AOFAS position statement regarding the future of the AOFAS Clinical Rating Systems. Foot and Ankle International. 2011.
  3. Button G, Pinney S. A meta-analysis of outcome rating scales in foot and ankle surgery: is there a valid, reliable, and responsive system?. Foot and Ankle International. 2004.
  4. SooHoo NF, Shuler M, Fleming LL. Evaluation of the validity of the AOFAS Clinical Rating Systems by correlation to the SF-36. Foot and Ankle International. 2003.

Editorial status

Not yet reviewedQueued for clinical review by Sam Tuffun, PT, DPT. Sign-off has not taken place — this is a placeholder assignment, not a completed review.