Fontaine Stage Interpreter
Fontaine Stage Interpreter
The four clinical stages of lower limb arterial disease, with the 200-metre sub-division that separates IIa from IIb and the published correspondence to the Rutherford categories — which is not a one-to-one map.
Fontaine stage
Four stages, IIa and IIb split at 200 mIntermittent claudication, pain-free walking distance 120 metres
Fontaine’s stages, and the published correspondence to Rutherford
| Fontaine | Clinical | Rutherford grade and category | Rutherford’s objective criterion |
|---|---|---|---|
| I | Asymptomatic | Grade 0, category 0 | Normal treadmill and reactive hyperaemia testing |
| IIa | Mild claudication — over 200 m, or over two flights | Grade I, category 1 | Absolute claudication distance over 200 m, recovery under 2 minutes; completes treadmill, post-exercise ankle pressure over 50 mmHg but at least 20 mmHg below resting |
| IIb | Moderate to severe claudication — under 200 m | Grade I, category 2 AND category 3 | Category 2 is defined only as between 1 and 3; category 3 cannot complete the treadmill, post-exercise ankle pressure under 50 mmHg |
| III | Ischaemic rest pain | Grade II, category 4 | Resting ankle pressure under 40 mmHg, toe pressure under 30 mmHg |
| IV | Ulceration or gangrene | Grade III, category 5 AND category 6 | Category 5 resting ankle pressure under 60 mmHg, toe pressure under 40 mmHg; category 6 the same criteria with tissue loss above the transmetatarsal level |
What Fontaine does not contain
| Element | Fontaine | Where it lives instead |
|---|---|---|
| Any pressure measurement | None | Rutherford’s objective criteria, and the ankle-brachial and toe-brachial indices |
| Minor against major tissue loss | Not distinguished | Rutherford categories 5 and 6 |
| Wound, infection and ischaemia grading | None | The SVS WIfI classification, a separate three-axis grading not built in this corpus |
| Lesion anatomy | None | The Trans-Atlantic Inter-Society Consensus morphological classes, which describe which lesions suit which repair |
| Acute limb ischaemia | Out of scope entirely | The separate Rutherford classification of acute limb ischaemia, categories I, IIa, IIb and III |
One number in the whole system, and it is self-reported
Fontaine’s classification is four clinical stages of chronic lower limb arterial disease, published by Fontaine, Kim and Kieny in 1954 and still in daily use because it needs nothing but a history. Stage I is asymptomatic arterial disease. Stage II is intermittent claudication, sub-divided at a walking distance. Stage III is ischaemic pain at rest. Stage IV is ulceration or gangrene. A limb takes the most advanced stage it meets, and each limb is staged separately.
The sub-division of stage II is the only quantitative element in the system, and it rests on something the patient says. The Central European Vascular Forum’s consensus document puts IIa at climbing more than two flights of stairs or walking more than 200 m and IIb at less than two flights or less than 200 m. Both halves of that are soft: a pain-free walking distance reported in a clinic is not the absolute claudication distance measured on a treadmill, flights of stairs vary, and the same document goes on to define severe claudication as less than one flight or less than 100 m while still calling it IIB. Fontaine has one bin where later systems have two.
Which is exactly why the correspondence with Rutherford is not a translation. The published table maps Fontaine I to Rutherford grade 0 category 0, IIa to grade I category 1, and III to grade II category 4 — three clean pairs. It then maps IIb to Rutherford categories 2 AND 3, and IV to categories 5 AND 6. Rutherford separates moderate from severe claudication on whether a standard treadmill test can be completed and on the post-exercise ankle pressure, and separates minor from major tissue loss on whether the loss extends above the transmetatarsal level. Fontaine collects neither fact. Counting IIa and IIb separately there are five Fontaine stages against seven Rutherford categories, so no one-to-one map is possible even in principle; the map from Rutherford to Fontaine is single-valued, and the map back is not.
Two things Fontaine is not. It is not a measurement, so it carries no pressure, no index and no image, and a stage should be recorded alongside an ankle or toe pressure rather than instead of one. And it is not the acute classification: the separate Rutherford categories for acute limb ischaemia use the labels IIa and IIb for something entirely different, and the Rutherford page sets both out side by side so they cannot be confused. This category owns the limb and the named vessel. Risk estimation in somebody with no vascular diagnosis belongs to the pooled cohort equations, the cost of an operation to the Revised Cardiac Risk Index and the AUB-HAS2 index, and central circulatory arithmetic to systemic vascular resistance and mean arterial pressure. The measurement technique decides the number before any threshold does: change the convention and the same limb, artery or aorta returns a different figure. Every threshold and interval here is attributed to the body that publishes it, those bodies disagree with one another, and your own service’s protocol takes precedence over all of them. This page computes a published index or places a finding in a published class. It recommends no action.
Frequently asked questions
What are the Fontaine stages of peripheral arterial disease?
Stage I asymptomatic; stage II intermittent claudication, sub-divided into IIa at a pain-free walking distance over 200 m and IIb under 200 m; stage III ischaemic pain at rest; stage IV ulceration or gangrene. The classification was published by Fontaine, Kim and Kieny in 1954 and is purely clinical.
Where exactly is the IIa to IIb boundary?
At 200 metres of pain-free walking, or two flights of stairs. The Central European Vascular Forum’s consensus document defines IIa as climbing more than two flights or walking more than 200 m and IIb as less than two flights or less than 200 m, and attaches an absolute claudication distance over 200 m with a recovery time under 2 minutes to the equivalent Rutherford category. Note that the self-reported distance and the treadmill distance are different measurements.
How do Fontaine stages map onto Rutherford categories?
Three stages map cleanly and two do not. Fontaine I is Rutherford grade 0 category 0, IIa is grade I category 1, and III is grade II category 4. But Fontaine IIb corresponds to Rutherford categories 2 and 3, and Fontaine IV to categories 5 and 6, because Rutherford makes distinctions — treadmill completion, post-exercise ankle pressure, the extent of tissue loss — that Fontaine never records. There are five Fontaine stages and seven Rutherford categories, so the map cannot be one-to-one.
Is Fontaine stage IIb the same as the IIb of acute limb ischaemia?
No, and this is a genuine source of error. The Rutherford classification of ACUTE limb ischaemia has its own categories I, IIa, IIb and III, graded on sensory loss and motor deficit, where IIb means an immediately threatened limb. Fontaine IIb means claudication at under 200 metres in chronic disease. The two share a label and nothing else.
Does a Fontaine stage tell you how severe the arterial disease is?
It tells you what the limb is doing, which is not the same thing. A limb can be stage I because the patient never walks far enough to claudicate — which is why the Rutherford standard attaches a normal treadmill test to its category 0 rather than relying on the history — and a limb with tissue loss is stage IV whether the loss is a single toe or the forefoot. A stage is a description of a limb at one moment, not a measurement.
Related calculators
References
- Andreozzi GM, Arosio E, Martini R, Verlato F, Visonà A. Consensus Document on Intermittent Claudication from the Central European Vascular Forum. Int Angiol. 2008;27(2):93–113.
- Articl. Rutherford Classification of Chronic Limb Ischemia, reproducing Rutherford RB, Baker JD, Ernst C, et al., J Vasc Surg. 1997;26(3):517–38.
- National Confidential Enquiry into Patient Outcome and Death. Acute Limb Ischaemia, chapter 3: The severity of acute limb ischaemia. London: NCEPOD, 2025.
- American Academy of Family Physicians. Management of Lower Extremity Peripheral Artery Disease: Guidelines From the ACC/AHA. Am Fam Physician. 2025;112(5).
- Radiopaedia. Ankle brachial index. Melbourne: Radiopaedia.org, 2025.
Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/