Circulation Basics

Your legs run three separate plumbing systems, and almost every confusing symptom below the knee comes down to which one is struggling. This section explains them in plain language.

Three systems in the leg: arteries deliver blood downward, veins return blood upward, lymph vessels drain excess tissue fluid Arteries — deliver blood to the foot Veins — return blood toward the heart Lymph vessels — drain excess tissue fluid
Three jobs, three directions. Each line is drawn in a different style as well as a different color, so the diagram still reads without color vision.

Why the distinction matters so much

A swollen, aching, discolored leg can be a vein problem, a lymphatic problem, a heart or kidney problem, a medication side effect, or something else entirely. An artery problem often looks like nothing at all until it suddenly does not. Treatments that help one can be actively unhelpful for another — compression is the clearest example, because it is a mainstay of vein care and can be risky when the arterial supply is poor.

So the useful question is rarely “do I have bad circulation?” It is “which system, and how badly?” That question has real answers, and they come from measurement rather than appearance.

Start with these

Then go where your symptoms point

  • PAD and arteries

    Blood not getting down to the foot. Leg pain on walking, cold feet, wounds that will not close.

    Read the PAD guide →

  • Veins and venous stasis

    Blood not getting back up. Heavy legs, swelling that improves overnight, skin changes at the ankle.

    Read the vein guide →

  • Swelling and lymphedema

    Fluid staying in the tissue. One leg or both, and a long list of possible causes.

    Read the swelling guide →

  • Tests and evaluation

    What an ABI actually measures, when ultrasound is the right test, and how to prepare.

    Read about testing →

A note on terminology

Medicine uses several words for overlapping things, which makes searching frustrating. Peripheral artery disease (PAD) and peripheral vascular disease (PVD) are often used interchangeably, though PVD is the broader term. Edema and edema are the same word with American and British spellings, as are lymphedema and lymphedema. Chronic venous insufficiency, venous stasis and venous hypertension all describe aspects of the same underlying problem. We use one page per subject rather than separate pages for each spelling.

If you are not sure where to start

Sources

  1. National Heart, Lung, and Blood Institute. Peripheral Artery Disease.
  2. Society for Vascular Surgery. Chronic Venous Insufficiency.
  3. NHS. Oedema.
  4. NHS. Lymphoedema.

Written by Tom Biernacki, DPM, FACFAS. Published 20 September 2026.