The popliteal vein course runs alongside the popliteal artery

Popliteal artery

In human anatomy, the popliteal artery is defined as the extension of the "superficial" femoral artery after passing through the adductor canal and adductor hiatus above the knee...

 but carries the blood from the knee joint and muscles in the thigh and calf back to the heart.

Its origin is defined by the junction of the posterior tibial vein

Posterior tibial vein

In anatomy, the posterior tibial vein of the lower limb carries blood from the posterior compartment and plantar surface of the foot to the popliteal vein which it forms when it joins with the anterior tibial vein....

 and anterior tibial vein

Anterior tibial vein

In human anatomy, the anterior tibial vein of the lower limb carries blood from the anterior compartment of the leg to the popliteal vein which is forms when it joins with the posterior tibial vein....

.

It drains the peroneal vein

Peroneal vein

In anatomy, the fibular veins are accompanying veins of the fibular artery.-Structure:...

 before reaching the knee

Knee

The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...

 joint and turns into the femoral vein

Femoral vein

In the human body, the femoral vein is a blood vessel that accompanies the femoral artery in the femoral sheath. It begins at the adductor canal and is a continuation of the popliteal vein...

 when leaving the adductor canal

Adductor canal

The adductor canal is an aponeurotic tunnel in the middle third of the thigh, extending from the apex of the femoral triangle to the opening in the Adductor magnus, the Adductor hiatus.-Boundary:...

 (also known as Hunter's canal).

The popliteal artery extends from the femoral artery

Femoral artery

The femoral artery is a general term comprising a few large arteries in the thigh. They begin at the inguinal ligament and end just above the knee at adductor canal or Hunter's canal traversing the extent of the femur bone....

 behind the popliteal fossa

Popliteal fossa

The popliteal fossa is a shallow depression located at the back of the knee joint. The bones of the popliteal fossa are the femur and the tibia.-Boundaries:The boundaries of the fossa are:-Roof:...

 which is the space behind the knee

Knee

The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...

.