Response of the popliteal artery to treadmill exercise and stress positioning in patients with and without exertional lower extremity symptoms

Key points

1. 01Limbs with exertional leg pain and neurologic symptoms showed a larger drop in ankle-brachial index 1 minute after running than symptom-free limbs.
2. 02On ultrasound, the below-knee popliteal artery narrowed more during maximal ankle plantar flexion in symptomatic limbs.
3. 03Running without incline triggered a stronger ankle-brachial index response than inclined walking, suggesting running is the better provocation test.
4. 04Compression of the artery and tibial nerve at the soleal sling (the popliteal outlet below the knee) may cause these symptoms more often than recognized.
5. 05Findings are exploratory, from one center, and cannot pinpoint exactly where the arterial flow reduction occurred.

How it was conducted

Design

Single-center, prospective, observational cohort study

Participants

15 symptomatic and 30 asymptomatic patients aged 18 to 55, recruited from vascular and orthopedic clinics; analyzed per limb (29 symptomatic, 61 asymptomatic limbs)

Groups

Limbs with ongoing exertional leg pain and neurologic symptoms vs symptom-free limbs

Tests

Duplex ultrasound popliteal artery diameter and peak systolic velocity at neutral and maximal plantar flexion; ankle-brachial index at rest and 1 and 5 minutes after walking (5 min, 3 mph, 10-degree incline) and running (5 min, 6 mph, 0-degree incline)

Primary outcome

Differences between symptomatic and asymptomatic limbs in popliteal artery response and exertional ankle-brachial index change

What they found

• Plantar flexion occluded the popliteal artery in 3 (10%) symptomatic and 5 (8.2%) asymptomatic limbs (P > .05).
• Mean popliteal artery diameter decrease in nonoccluding arteries was 2.4 +/- 0.34 mm in symptomatic vs 1.6 +/- 0.21 mm in asymptomatic limbs (P = .02).
• Peak systolic velocity increased by a mean of 49 cm/s in symptomatic and 65 cm/s in asymptomatic limbs with flexion (P > .05).
• At 1 minute after running, 25 (86%) symptomatic limbs vs 31 (51%) asymptomatic limbs had an ankle-brachial index decrease of at least 0.01 (P = .001).
• Mean absolute ankle-brachial index change 1 minute after running was -0.18 in symptomatic vs -0.02 in asymptomatic limbs (P < .0001), a 16% vs 2% change from baseline (P < .0001).

Limitations

• The exertional ankle-brachial index drop is not specific for where the arterial flow reduction occurs, and anatomic forms of entrapment (types I to V) could not be ruled out.
• Imaging examined only the below-knee popliteal outlet, not the entire artery course; popliteal veins were not assessed.
• The symptomatic group had undifferentiated symptoms that were not categorized by pattern.
• Small, single-center observational study with no surgical or clinical-outcome correlation.

Why it matters

For patients

If you are young and active with exertional leg pain that does not fit usual diagnoses, a treadmill ankle-brachial index test and ankle-positioning ultrasound may help find a treatable cause.

For clinicians

Consider exertional ankle-brachial index with treadmill running plus dynamic below-knee popliteal ultrasound when evaluating fit patients with exertional leg pain to screen for functional popliteal entrapment at the popliteal outlet.

For readers

This early study links simple noninvasive vascular tests to exertional leg symptoms, but larger studies with comprehensive imaging are needed before the tests can be considered diagnostic.