Popliteal Artery Injury

First aid

1. Call 911 or your local emergency number.
2. Control bleeding with firm direct pressure; use a tourniquet above the knee for life-threatening bleeding that pressure cannot stop.
3. Keep the leg still and supported in the position found; do not try to straighten a deformed knee.
4. Do not apply ice packs to a cold, pale foot, and do not elevate a limb that may have poor blood flow.
5. Note the time of injury; it matters for surgery.

Why the popliteal artery is vulnerable

The popliteal artery is the continuation of the femoral artery as it passes behind the knee, before splitting into the arteries of the lower leg. It is held firmly in place above (at the adductor hiatus) and below (at the soleus arch). When the knee dislocates, the artery cannot move out of the way, so it is stretched, its inner lining tears, or it is cut. An inner lining tear can lead to a clot that blocks the artery hours later, even if pulses seem normal at first.

The collateral circulation around the knee is poor, so blocking the popliteal artery often leaves the lower leg without enough blood.

Causes

• Knee dislocation: the classic cause. Arterial injury occurs in a substantial minority, in some series up to about a third. Many knee dislocations reduce spontaneously before arrival at the hospital, so they can be missed.
• Fractures: of the lower thigh bone or upper shin bone, see knee fracture.
• Penetrating trauma: gunshot and stab wounds.
• Crush injuries and high-energy accidents.
• Surgery: rarely, during knee replacement, ligament reconstruction or arthroscopy.

Signs and symptoms

Hard signs (need immediate surgery)

• absent pulses in the foot
• active, pulsatile bleeding
• a rapidly expanding or pulsating swelling behind the knee
• a palpable thrill or audible bruit over the area
• signs of limb ischemia: pain, pallor, paralysis, numbness, and coldness

Soft signs (need urgent testing)

• reduced but present pulses
• a stable bruise or swelling
• nerve injury near the artery (the tibial or peroneal nerve; the peroneal nerve is injured in many knee dislocations, causing foot drop)
• a history of significant bleeding at the scene

Diagnosis

• Pulse examination of the foot, repeated over time.
• Ankle-brachial index (ABI): the blood pressure at the ankle divided by that at the arm. An ABI below 0.9 after knee dislocation suggests arterial injury and needs imaging. An ABI of 0.9 or above with normal pulses is reassuring, but serial exams are still done.
• CT angiography: the main imaging test to show the site and type of injury.
• Catheter angiography: in the operating room or for endovascular treatment.

Treatment

• Emergency surgery: repair of the artery, or a bypass using a vein graft from the other leg. A temporary shunt may restore flow while bones are stabilized.
• Fasciotomy: cutting the tight muscle compartments of the calf to prevent or treat compartment syndrome, which commonly follows restored blood flow.
• Stabilization: an external fixator holds the knee in place while the repair heals.
• Endovascular options: stents in selected stable patients.
• Later surgery for knee ligament reconstruction.
• Rehabilitation: physical therapy for knee stiffness, nerve injury and walking.

Complications

• amputation, especially when blood flow is restored after 6 to 8 hours
• compartment syndrome and muscle death
• nerve damage with foot drop
• graft blockage or infection
• long-term knee stiffness and instability

Outlook

With rapid recognition and repair, most limbs are saved. The longer the leg is without blood flow, the worse the outcome. Many people have lasting knee problems from the ligament damage that accompanies dislocation.

Frequently asked questions

Why is a knee dislocation an emergency?

A knee dislocation can stretch or tear the popliteal artery behind the knee, cutting off blood flow to the lower leg. Without prompt repair, the leg can be lost. Even if the knee pops back in, it needs emergency assessment.

What are the signs of a popliteal artery injury?

Signs include a cold, pale or bluish foot, weak or absent foot pulses, severe pain, numbness, weakness, active bleeding or a growing swelling behind the knee. Some injuries cause a clot hours later, so repeated checks are important.

How is a popliteal artery injury diagnosed?

Doctors check foot pulses and measure the ankle-brachial index. If the index is low or pulses are abnormal, CT angiography shows the injury. Hard signs, such as absent pulses with a cold foot, lead straight to surgery.

Can you recover from a popliteal artery injury?

Yes. Most people keep their leg when blood flow is restored quickly. Recovery often involves several operations, physical therapy and months of rehabilitation, particularly for the knee ligaments and any nerve damage.