Ankle-brachial index: Definition, Uses, and Clinical Overview

Ankle-brachial index Introduction (What it is)

Ankle-brachial index is a simple ratio comparing blood pressure at the ankle to blood pressure in the arm.
It is commonly used to screen for reduced blood flow to the legs, often related to peripheral artery disease (PAD).
Clinicians use it in vascular medicine, primary care, and perioperative (before-surgery) evaluation.
It can also help orthopedic teams understand whether circulation might affect pain, healing, or rehab tolerance.

Why Ankle-brachial index used (Purpose / benefits)

Ankle-brachial index is used to detect or suggest problems with arterial blood flow to the lower limbs. Arteries are the “high-pressure” blood vessels that deliver oxygen-rich blood to tissues. When arteries narrow or stiffen, leg muscles and skin may not receive adequate blood during activity or healing.

Key purposes and benefits include:

• Screening for peripheral artery disease (PAD): PAD is a common cause of leg symptoms and impaired wound healing. Ankle-brachial index is a widely used first-line test because it is noninvasive and relatively quick.
• Clarifying the source of leg pain: Leg pain with walking can come from multiple systems—musculoskeletal (hip/knee arthritis, tendon problems), neurologic (lumbar spinal stenosis), or vascular (PAD-related claudication). Ankle-brachial index adds objective information about blood flow.
• Risk stratification and surgical planning: In orthopedic and sports medicine settings, circulation matters for healing after fractures, tendon/ligament surgery, joint replacements, and management of chronic ulcers. Ankle-brachial index can be part of assessing whether vascular evaluation is needed.
• Establishing a baseline and monitoring trends: A measured index provides a reproducible baseline that can be compared over time, recognizing that interpretation and follow-up plans vary by clinician and case.

This test does not “treat” a condition. It supports decision-making by helping detect reduced perfusion (blood delivery) to the legs.

Indications (When orthopedic clinicians use it)

Orthopedic, sports medicine, and rehabilitation clinicians may consider Ankle-brachial index in situations such as:

• Leg pain or cramping with walking that improves with rest (possible vascular claudication)
• Nonhealing wounds, slow incision healing, or recurrent skin breakdown in the foot/ankle or lower leg
• Cold feet, color changes, reduced hair growth, or other signs suggesting reduced circulation
• Diminished or hard-to-find foot pulses on physical exam
• Preoperative assessment when circulation could affect healing (for example, complex foot/ankle reconstruction or high-risk lower-extremity procedures)
• Differentiating vascular causes of symptoms from hip osteoarthritis, hip tendon problems, lumbar radiculopathy, or spinal stenosis
• Evaluation after lower-extremity trauma when vascular compromise is a concern (often alongside other assessments)

Contraindications / when it’s NOT ideal

Ankle-brachial index is noninvasive, but there are scenarios where it may be unreliable, difficult to perform, or not the preferred first test:

• Noncompressible arteries (calcified vessels): In some people (commonly older adults and those with diabetes or chronic kidney disease), arteries may be stiff and hard to compress with a cuff. This can produce an artificially high Ankle-brachial index and reduce accuracy.
• Significant wounds or dressings at cuff/measurement sites: Open ulcers, recent skin grafts, burns, or bulky postoperative dressings around the ankle may limit correct cuff placement or Doppler access.
• Severe leg swelling or lymphedema: Marked edema can make cuff measurements less reliable or uncomfortable.
• Severe pain with cuff inflation or inability to remain still: Movement can affect readings.
• Urgent limb-threatening symptoms: In suspected acute limb ischemia (sudden severe pain, pallor, pulselessness, or neurologic changes), clinicians may prioritize urgent vascular evaluation rather than a routine Ankle-brachial index workflow. The best approach varies by clinician and case.
• Certain rhythm abnormalities (for automated devices): Irregular heart rhythms can interfere with oscillometric (automatic) blood pressure measurements, sometimes making Doppler-based methods preferable.

When standard Ankle-brachial index is limited, clinicians may use related tests such as toe-brachial index, duplex ultrasound, or other vascular studies.

How it works (Mechanism / physiology)

Ankle-brachial index relies on a basic physiologic principle: in healthy arteries, systolic blood pressure measured at the ankle is typically similar to (or slightly higher than) the systolic pressure measured at the arm. If there is significant narrowing (stenosis) or blockage in the arteries supplying the leg, the ankle systolic pressure may be lower relative to the arm.

What the measurement reflects

• Brachial pressure (arm): A cuff and measurement at the brachial artery provides a reference systemic blood pressure.
• Ankle pressure (leg): A cuff at the ankle measures systolic pressure in arteries supplying the foot, commonly the dorsalis pedis and posterior tibial arteries.
• The ratio (ankle ÷ arm): This ratio is the Ankle-brachial index. Lower ratios can suggest reduced arterial perfusion to the leg.

Relevant anatomy and why orthopedics may care

While Ankle-brachial index is not a “hip test,” it connects to orthopedic care through the shared anatomy and function of the lower limb:

• Major inflow vessels to the leg: Blood travels through the aorta → iliac arteries (in the pelvis) → femoral artery (groin/thigh) → popliteal artery (behind knee) → tibial arteries (lower leg) → foot arteries.
• Tissues affected by reduced flow: Muscles used for walking, skin and subcutaneous tissue, and—indirectly—bone and surgical sites may be impacted when perfusion is poor.
• Symptom overlap with hip and spine conditions: Vascular claudication can cause buttock, thigh, or calf discomfort during walking, sometimes mimicking hip joint pain or lumbar spinal stenosis patterns. Clinical evaluation typically integrates history, exam, and appropriate testing.

Onset, duration, and reversibility

Ankle-brachial index does not have an “onset” like a medication. It is a measurement that provides a snapshot of arterial perfusion at the time of testing. Results can change over time due to disease progression, improved conditioning, changes in blood pressure, or vascular interventions. How often it is repeated varies by clinician and case.

Ankle-brachial index Procedure overview (How it’s applied)

Ankle-brachial index is a diagnostic test, not a surgical procedure. A typical high-level workflow looks like this:

1. Evaluation / exam – A clinician reviews symptoms (pain with walking, wounds, numbness), medical history, and risk factors. – Foot pulses and skin changes may be checked.

2. Preparation – The person typically rests lying down for a short period so pressures stabilize. – Cuffs are selected to fit the arm and ankle correctly, since cuff size can affect readings.

3. Testing – Arm pressure: Systolic pressure is measured in one or both arms. – Ankle pressure: Systolic pressure is measured at the ankle using:

   • A handheld Doppler probe (common in many clinics), or
   • An automated oscillometric device (common in some offices).
   • Measurements may be taken from more than one ankle artery to improve accuracy.

4. Immediate checks – The clinician confirms signals/readings are adequate and repeats measurements if needed. – The Ankle-brachial index is calculated and documented.

5. Follow-up – Results are interpreted in context. Commonly used interpretive categories include:

   • Normal: often cited around 1.0 to 1.4
   • Suggestive of PAD: often cited below about 0.9
   • Severe reduction: lower values may indicate more significant disease
   • Noncompressible / potentially unreliable: often cited above about 1.3 to 1.4
     Exact cutoffs and next steps can vary by clinician and case.

• If needed, additional vascular testing may be considered (for example, exercise Ankle-brachial index or imaging).

Types / variations

Clinicians may use different versions of Ankle-brachial index–based assessment depending on the clinical question and patient factors:

• Resting Ankle-brachial index
• Performed at rest, typically supine.

• Often used as an initial screen for PAD.

• Exercise Ankle-brachial index

• Pressures are measured before and after walking on a treadmill or performing a standardized exercise.

• Can help reveal flow limitations that are not obvious at rest, especially when symptoms occur only with activity.

• Toe-brachial index (TBI)

• Uses toe systolic pressure instead of ankle pressure.

• Often considered when ankle arteries are noncompressible (for example, due to calcification).

• Segmental pressures and pulse volume recordings (PVR)

• Uses multiple cuffs along the leg and waveform assessment to help localize the level of arterial disease (thigh vs calf vs ankle).

• Doppler-based vs oscillometric (automated) methods

• Handheld Doppler is commonly used and can be helpful when pulses are difficult to palpate.
• Automated devices can be faster in some settings but may be more sensitive to motion or rhythm issues.

Pros and cons

Pros:

• Noninvasive and generally well-tolerated
• Quick to perform in many outpatient settings
• Provides an objective number that can be tracked over time
• Helpful for screening and for supporting a PAD diagnosis alongside symptoms and exam
• Can assist in distinguishing vascular limitations from musculoskeletal or neurologic causes of leg symptoms
• May inform risk assessment related to lower-extremity healing and rehabilitation planning

Cons:

• Can be inaccurate in noncompressible/calcified arteries, sometimes producing falsely elevated values
• Does not pinpoint the exact location of arterial narrowing without additional testing
• May be less informative when symptoms are complex (for example, mixed hip arthritis plus spinal stenosis plus PAD)
• Results can be affected by technique (cuff size/placement, patient position, movement)
• Exercise-related symptoms may require exercise testing even if resting values appear normal
• It is a screening/physiologic measure and does not replace vascular imaging when imaging is indicated

Aftercare & longevity

Because Ankle-brachial index is a measurement rather than a treatment, “aftercare” is usually minimal:

• Immediate recovery: Most people resume normal activity right away, since the test involves cuff inflation and pressure readings only.
• What affects the usefulness of the result:
• Disease severity and symptom pattern: Resting values may not fully explain exertional symptoms in some cases.
• Comorbidities: Diabetes, chronic kidney disease, and advanced age can increase the chance of noncompressible arteries, affecting accuracy.
• Technique and setting: Proper cuff sizing, standardized positioning, and use of Doppler when needed can improve reliability.
• Blood pressure variability: Systemic blood pressure changes can influence the ratio and interpretation.
• Longevity of results: The result reflects circulation at the time of testing. Whether and when it should be repeated depends on the clinical context, symptom changes, and clinician preference—varies by clinician and case.
• Rehabilitation and orthopedic planning considerations: If reduced perfusion is suspected or confirmed, orthopedic teams may factor circulation into timelines for wound monitoring, conditioning progression, and overall risk discussion, typically in coordination with the broader care team.

Alternatives / comparisons

Ankle-brachial index is one tool among several for evaluating leg symptoms and circulation. Common alternatives or complementary approaches include:

• Clinical history and physical exam
• Pulse checks, skin temperature/color, capillary refill, and symptom description are foundational.

• Limitations: physical exam alone can miss early PAD or be difficult when swelling or body habitus obscures pulses.

• Toe-brachial index

• Often compared with Ankle-brachial index when arteries are noncompressible at the ankle.

• Can provide useful information in patients where ABI is falsely high.

• Duplex ultrasound

• Combines ultrasound imaging with flow assessment to visualize arteries and detect narrowing.

• Often used when ABI is abnormal or symptoms are significant, since it can help localize disease.

• CT angiography (CTA) or MR angiography (MRA)

• Imaging studies that map arterial anatomy in more detail.

• Typically considered when planning interventions or when noninvasive tests are inconclusive; selection depends on patient factors and clinical goals—varies by clinician and case.

• Pulse volume recordings (PVR) and segmental pressures

• Provide waveform and level-specific information, complementing ABI for localization.

• Orthopedic and neurologic evaluation for symptom overlap

• Hip osteoarthritis, trochanteric pain, stress injuries, tendinopathies, and lumbar spinal stenosis can mimic or coexist with vascular symptoms.
• Comparing findings across systems (vascular, musculoskeletal, neurologic) is often necessary rather than relying on a single test.

Ankle-brachial index Common questions (FAQ)

Q: Does Ankle-brachial index testing hurt?
Most people describe it as mild pressure from the blood pressure cuffs. The cuff inflation can be briefly uncomfortable, similar to a standard arm blood pressure check. Pain levels vary by individual sensitivity and the presence of wounds or swelling.

Q: How long does the test take?
In many clinics, a resting Ankle-brachial index can be completed in a short visit. Extra time may be needed if both legs and both ankle arteries are measured, if readings must be repeated, or if an exercise component is added.

Q: What do “normal” and “abnormal” results generally mean?
In many references, values around 1.0 to 1.4 are considered within a typical range, while lower values can suggest PAD. Higher-than-expected values can occur when ankle arteries are noncompressible, making the result less reliable. Exact interpretation and thresholds can vary by clinician and case.

Q: Can Ankle-brachial index explain hip pain?
It does not diagnose hip joint problems such as arthritis, labral tears, or bursitis. However, it can help identify whether reduced blood flow could be contributing to exertional leg symptoms that sometimes feel like hip or thigh discomfort. Hip pain often requires a separate musculoskeletal assessment.

Q: If my Ankle-brachial index is low, does that automatically mean I need a procedure?
Not necessarily. Ankle-brachial index is a screening and assessment tool, and next steps depend on symptoms, functional limitations, wound status, and overall health. Further evaluation may involve additional physiologic tests or imaging—varies by clinician and case.

Q: How long do the results “last”?
The number reflects blood flow conditions at the time of testing. It may remain similar over time or change with progression of vascular disease, changes in blood pressure, or after vascular treatment. Repeat testing frequency depends on symptoms and clinical context—varies by clinician and case.

Q: Is the test safe?
For most people, Ankle-brachial index is low risk because it is noninvasive and uses external cuffs and (often) Doppler ultrasound. Limitations are mainly related to discomfort, measurement accuracy in certain conditions, or difficulty testing over wounds or severe swelling.

Q: Can I drive, work, or exercise afterward?
Because it is a diagnostic measurement without sedation, people can typically return to usual activities immediately. If an exercise Ankle-brachial index is performed, there may be brief fatigue from walking. Activity guidance, if any, depends on the broader clinical situation—varies by clinician and case.

Q: Will I need to remove braces, compression garments, or shoes?
The ankle cuff and Doppler measurement require access to the lower leg/ankle and usually the foot arteries. Some items may need to be removed or adjusted to place the cuff correctly and locate signals. What is required depends on the device used and the measurement sites.

Q: Why might a clinician order additional testing even if my Ankle-brachial index is “normal”?
Resting values can be normal in some people who only develop symptoms during exertion, or when disease is mild or localized. If symptoms strongly suggest a circulation issue, clinicians may consider exercise testing, toe pressures, duplex ultrasound, or other studies. The choice depends on the question being asked and patient factors—varies by clinician and case.