The lower limbs receive their blood supply from the abdominal aorta, which splits into two common iliac arteries at about the level of the fourth lumbar vertebra, slightly left of the midline. From that single branching point, a continuous chain of arteries carries blood down through the thigh, knee, lower leg, and foot, changing names at specific anatomical landmarks along the way. A parallel set of deep veins returns that blood to the heart.
The Iliac Arteries: Where Supply Begins
The two common iliac arteries diverge as they descend from the aorta. At the level of each sacroiliac joint, they split again into an internal iliac artery and an external iliac artery. The internal iliac artery turns inward to supply the pelvic organs, gluteal muscles, and surrounding structures. The external iliac artery continues downward toward the leg.
Once the external iliac artery passes beneath the inguinal ligament (the crease where your thigh meets your torso), it becomes the femoral artery. This transition point is where clinicians check the femoral pulse, palpated just below the inguinal ligament, roughly a third of the way from the pubic bone toward the outer hip.
The Femoral Artery and Deep Thigh Supply
The femoral artery is the primary blood supply to the thigh. It runs down the inner front of the upper leg, and shortly after entering the thigh it gives off a major branch called the deep femoral artery (profunda femoris). This deep branch is the workhorse of the thigh. Its perforating branches supply the hamstrings on the back of the thigh, including the biceps femoris, semitendinosus, and semimembranosus, as well as much of the surrounding musculature.
At rest, the femoral artery delivers roughly 636 milliliters of blood per minute to each leg, based on measurements from the American Heart Association. That flow increases dramatically during exercise as muscles demand more oxygen.
The femoral artery also gives off a descending genicular branch near the knee, which plays a role in the network of vessels around the knee joint. The main trunk of the femoral artery continues downward through a tunnel in the thigh muscles called the adductor canal. When it emerges through an opening at the bottom of that canal (the adductor hiatus, a gap in the adductor magnus muscle), it enters the space behind the knee and takes a new name: the popliteal artery.
The Popliteal Artery and Knee Region
The popliteal artery sits deep in the popliteal fossa, the soft area behind your knee. Its pulse can be felt there, slightly to the outer side of the midline, though it takes firm pressure because the vessel lies deep beneath muscle and fat.
Before splitting into its terminal branches, the popliteal artery sends off five genicular branches that form a network of connections around the knee. These include the superior and inferior medial genicular arteries, the superior and inferior lateral genicular arteries, and a middle genicular artery. Together with contributions from the descending genicular artery above and the anterior tibial recurrent artery below, they create an anastomosis, a web of interconnected vessels that supplies the knee joint and surrounding tissues. This network also serves as a backup route: if the main artery through the thigh becomes blocked (as happens in peripheral artery disease), blood can reroute through these smaller connections to reach the lower leg.
Three Arteries of the Lower Leg
Below the knee, the popliteal artery divides into three vessels that supply the lower leg:
- Anterior tibial artery: Passes forward through a gap in the membrane between the two leg bones and runs down the front of the shin. It supplies the muscles in the anterior compartment, the ones that lift your foot and toes.
- Posterior tibial artery: Continues down the back of the calf, supplying the deep posterior muscles. Its pulse can be felt just behind the bony bump on the inner ankle (the medial malleolus), though this is considered the most difficult lower limb pulse to locate.
- Fibular (peroneal) artery: Branches from the posterior tibial artery and runs along the outer side of the back of the leg, supplying the lateral compartment muscles.
Even when these arteries show anatomical variations in their branching pattern, they consistently supply the expected compartments: the anterior tibial artery feeds the front of the leg, and the posterior tibial and fibular arteries feed the back and outer side.
Blood Supply to the Foot
When the anterior tibial artery crosses the front of the ankle joint, midway between the two ankle bones, it becomes the dorsalis pedis artery. This vessel runs along the top of the foot over the bones of the midfoot. You can feel its pulse on the top of your foot, about 1 centimeter from the bony prominence of the navicular bone, lateral to the tendon that extends the big toe. About 10% of people lack a detectable dorsalis pedis pulse due to normal anatomical variation, not disease.
The dorsalis pedis artery gives off several branches that fan across the top of the foot, including the arcuate artery and the medial and lateral tarsal arteries. At the base of the first toe space, the dorsalis pedis dives downward between the bones to connect with the sole of the foot.
The sole receives its supply primarily from the posterior tibial artery, which splits into the medial and lateral plantar arteries after passing behind the inner ankle. The lateral plantar artery forms the plantar arch, a curved vessel across the sole that connects with the deep branch of the dorsalis pedis artery from above. This connection creates a loop, ensuring blood reaches the toes from multiple directions.
Deep Veins: Returning Blood to the Heart
The venous system of the lower limb mirrors the arterial system closely. Deep veins run alongside their corresponding arteries and generally share their names. In the calf, the anterior tibial, posterior tibial, and peroneal veins travel as paired vessels that wrap around their companion arteries in a mesh-like arrangement. Muscle veins within the calf, particularly in the soleus and gastrocnemius muscles, also drain into this deep system.
These calf veins merge to form the popliteal vein behind the knee. The popliteal vein continues upward through the adductor canal as the femoral vein. The deep femoral vein, draining the thigh muscles, connects directly to the popliteal vein in about 38% of people, and through a tributary in another 48%.
The femoral vein joins with the internal iliac vein (draining the pelvis) to form the common iliac vein on each side. The two common iliac veins unite at the right side of the fifth lumbar vertebra to form the inferior vena cava, which carries blood back to the heart. One quirk of this anatomy: the left common iliac vein gets compressed between the overlying right common iliac artery and the spine, a finding visible on imaging in about half of all people.
In addition to the deep veins, superficial veins sit above the muscle layer and drain the skin and tissue just beneath it. Perforating veins connect the superficial and deep systems, directing blood inward toward the deep veins. The classic textbook arrangement of all these veins may be present in as few as 16% of limbs, making significant variation the norm rather than the exception.
Where to Check for Pulses
Four pulse points in the lower limb give a quick snapshot of blood flow at different levels:
- Femoral pulse: Below the inguinal ligament, about a third of the way from the pubic bone toward the outer hip bone.
- Popliteal pulse: In the popliteal fossa behind the knee, slightly lateral to center. Requires firm, deep pressure.
- Posterior tibial pulse: Just behind the medial malleolus (inner ankle bone).
- Dorsalis pedis pulse: On the top of the foot, lateral to the big toe’s extensor tendon, near the navicular bone.
Checking these pulses sequentially from top to bottom helps localize where a blockage or narrowing might be. A strong femoral pulse with a weak or absent foot pulse, for example, suggests a problem somewhere between the groin and the ankle.