There frequently are anatomical variations of the popliteal vein. Surgeons need to be aware of these variations when posteriorly approaching the knee. The popliteal vein is also significant as one of the primary locations of deep vein thrombosis (DVT) occurrence.
Anatomy
The popliteal vein is a deep vein of the lower leg. A normal popliteal vein has a diameter of 5 to 13 millimeters (mm), with males tending to have larger diameters and females smaller diameters.
Location
The anatomical region where the popliteal vein is located is called the popliteal fossa. The popliteal fossa is a diamond-shaped area at the back of the knee, which you might think of as the “pit” of your knee.
The popliteal fossa is bordered by the biceps femoris muscle on the upper outer side (proximolaterally), the semimembranosus and semitendinosus muscles on the upper inner side (proximomedially), and the two heads of the gastrocnemius muscle on the lower sides (distally).
Located within the popliteal fossa, from the inner (medial) side to the outer (lateral) side, are the:
Popliteal artery Popliteal vein Tibial nerve
Blood flows into the popliteal vein from multiple tributaries in the lower leg, including the:
Anterior tibial vein Posterior tibial vein Small saphenous vein Genicular veins Sural veins Peroneal veins
The popliteal vein itself originates where the anterior and posterior tibial veins join together, at the back of the knee. From there, the popliteal vein runs through the popliteal fossa.
In most people, the popliteal vein runs closer to the skin’s surface (superficially) than the popliteal artery. Within the popliteal fossa, the popliteal vein typically runs laterally to the popliteal artery.
As the popliteal vein travels up, it passes through the adductor hiatus, which is a gap in the adductor magnus muscle at the inner thigh. At this point, it is renamed the femoral vein. The femoral vein turns into the external iliac vein, which drains into the common iliac vein before returning to the heart.
Anatomical Variations
Like other vessels of the lower leg, there are common anatomical variations of the popliteal vein. The probability and types of anatomical variations are actually a large area of research.
Surgeons must be aware of these variations in order to keep patients safe as they cut into the back of the knee, accurately interpret computed tomography (CT) images and ultrasounds, and plan interventions.
Some commonly studied anatomical variations of the popliteal vein include:
High origin: In 18. 7% of studied cases, there was a higher-than-normal origin, located slightly below the adductor hiatus. Duplication: The popliteal vein is duplicated completely in 7. 8% of cases. Incomplete duplication is seen as the popliteal vein splits into two (15. 6%) or three (3. 1%) tributaries as it travels through the popliteal fossa. A study of CT venography found one side is typically dominant (has a higher blood flow) in cases of duplication or splitting. Single vein: A rare variation found in 4. 7% of cases in one study and 0. 7% of cases in another study is a singular persistent sciatic vein instead of a popliteal and femoral vein. Course: The position and course of the popliteal vein in comparison to the popliteal artery can also vary. Instead of the typical lateral position to the popliteal artery, in some people the popliteal vein crosses over it either medially or laterally (toward the inner or outer sides of the knee).
Function
The function of the popliteal vein is to drain deoxygenated blood from the lower leg and bring it back to the heart for oxygenation.
Specifically, the popliteal vein provides venous return for the gastrocnemius muscle. The gastrocnemius is the large, two-headed muscle on your calf that helps you move your leg back as you walk.
Blood is returned to the heart through a series of veno-muscular pumps. The gastrocnemial pump is particularly important because when you walk, the contraction pushes a “jet” of blood directly into the popliteal vein.
Clinical Significance
The popliteal vein has clinical significance for some vascular health conditions, including conditions that require emergency treatment.
Deep Vein Thrombosis
The popliteal vein is one of the most common locations for a deep vein thrombosis (DVT), or blood clot within a vein, to occur. This is very dangerous as there is a risk of the blood clot breaking free and traveling to the heart or lungs and causing a pulmonary embolism (PE).
In the case of a stroke where no cause is identified, it is also recommended to perform an ultrasound to investigate a possible DVT. Most people diagnosed with a DVT will be prescribed warfarin or another anticoagulant and closely monitored by a physician. In some acute cases, vascular surgery is required.
Popliteal Venous Aneurysm
Venous aneurysms are rare, but a popliteal venous aneurysm (PVA) is the most common type. In an aneurysm, a vein wall weakens, which can lead to DVT or PE. PVA is most common in people ages 50 to 59 and is usually asymptomatic. It is discovered with CT scans and on routine investigations of varicose veins.
Popliteal Vein Entrapment
In rare cases, the popliteal vein may become compressed due to a muscular anomaly, popliteal artery aneurysm, enlarged gastrocnemius (calf muscle) in athletes, or other reasons. This can result in lower leg edema (swelling) and even a secondary DVT.
Posterior Approach Knee Surgery
To avoid significant hemorrhage or injury, it is essential for surgeons to know the anatomy and location of a person’s popliteal vein when cutting from the back of the knee.
Although an anterior (frontal) approach is more common, surgeries that require a posterior approach include repair of the neurovascular bundle, avulsion fractures from the posterior cruciate ligament (PCL), gastrocnemius muscle recession, hamstring lengthening, and Baker cyst excision.
