The popliteal artery is a continuation of the femoral artery and is the main blood vessel supplying the knee region and lower leg. It is an essential artery that provides oxygenated blood to the structures in the posterior region of the knee and beyond.
Location
The popliteal artery begins at the adductor hiatus, a gap in the adductor magnus muscle, where the femoral artery transitions into the popliteal artery. It runs through the popliteal fossa, a shallow depression located at the back of the knee joint. The artery travels deep within the fossa, positioned posterior to the knee joint and adjacent to the tibial nerve. It continues downward along the posterior aspect of the knee before branching into the anterior tibial artery and posterior tibial artery at the lower border of the popliteus muscle, just below the knee.
Structure and Anatomy
Origin
The popliteal artery is a direct continuation of the femoral artery, which transitions into the popliteal artery as it passes through the adductor hiatus, an opening in the adductor magnus muscle. This transition occurs in the distal thigh, just above the knee joint. The artery continues its course through the popliteal fossa, a shallow, diamond-shaped depression located at the back of the knee.
Course
After originating at the adductor hiatus, the popliteal artery travels downward through the popliteal fossa. The artery is positioned deep within the fossa, beneath the tibial nerve and the popliteal vein, making it the deepest structure in the fossa. It is bordered by muscles and tendons that provide protection and facilitate its role in delivering blood to the knee and lower leg. As it moves distally, the popliteal artery courses toward the lower border of the popliteus muscle, where it eventually bifurcates into the anterior tibial artery and posterior tibial artery.
Branches
The popliteal artery gives rise to several important branches as it courses through the popliteal fossa, each contributing to the blood supply of the knee joint, surrounding muscles, and other soft tissues:
- Superior Medial and Superior Lateral Genicular Arteries: These arteries arise from the popliteal artery near the upper portion of the popliteal fossa and supply the distal femur and parts of the knee joint. They participate in the formation of the genicular anastomosis, a network of arteries around the knee that ensures continuous blood flow to the joint.
- Middle Genicular Artery: This small but important artery arises directly from the popliteal artery and penetrates the posterior aspect of the knee joint, supplying the cruciate ligaments, synovial membrane, and other intra-articular structures of the knee.
- Inferior Medial and Inferior Lateral Genicular Arteries: These arteries branch off near the lower part of the popliteal fossa and supply the proximal tibia, fibula, and parts of the knee joint. Like the superior genicular arteries, they contribute to the genicular anastomosis.
- Sural Arteries: These branches arise from the popliteal artery and supply blood to the gastrocnemius, soleus, and plantaris muscles. The sural arteries are responsible for nourishing the calf muscles and aiding in their function.
Termination
At the lower border of the popliteus muscle, the popliteal artery terminates by bifurcating into two major arteries:
- Anterior Tibial Artery: This artery passes through the interosseous membrane and supplies the anterior compartment of the leg.
- Posterior Tibial Artery: This artery continues down the posterior compartment of the leg and eventually supplies the plantar surface of the foot.
Anatomical Relations
The popliteal artery is the deepest structure within the popliteal fossa, situated posterior to the knee joint. It lies anterior to the popliteal vein and the tibial and common fibular nerves, which are located more superficially. The artery is flanked by the muscles of the leg, including the gastrocnemius and plantaris muscles on its posterior side and the popliteus muscle on its anterior side. This positioning provides protection and support for the artery, ensuring that it can perform its function while being shielded from direct trauma.
Genicular Anastomosis
The popliteal artery plays a key role in forming the genicular anastomosis, a network of arteries that surrounds the knee joint and ensures adequate blood flow to this highly mobile joint. The anastomosis includes the superior and inferior genicular arteries (both medial and lateral) as well as contributions from other arteries such as the descending genicular artery from the femoral artery. This network allows for collateral circulation in case of arterial blockage or constriction, ensuring that the knee joint remains well-perfused during various movements and positions.
Surface Anatomy and Palpation
The popliteal artery is deep within the popliteal fossa and can be difficult to palpate. However, in certain cases, the popliteal pulse can be felt by pressing deeply into the fossa while the knee is slightly flexed, making it an important site for assessing blood flow in the lower extremity. The artery is well-protected by surrounding muscles and tissues, reducing its exposure to injury.
Function
Blood Supply to the Knee Joint
The popliteal artery is the primary blood vessel responsible for supplying oxygenated blood to the knee joint. Through its branches, the artery provides blood to various components of the knee, including the bones, ligaments, and cartilage. Several branches of the popliteal artery—specifically the superior medial, superior lateral, inferior medial, and inferior lateral genicular arteries—form a network known as the genicular anastomosis. This network ensures continuous blood supply to the knee joint, particularly during flexion, when other arteries may become temporarily compressed.
- Superior Medial and Lateral Genicular Arteries: These supply blood to the femur and the surrounding soft tissue structures of the knee joint.
- Inferior Medial and Lateral Genicular Arteries: These branches supply blood to the tibia and fibula, as well as the ligaments and other structures in the lower portion of the knee.
Through this complex vascular network, the popliteal artery helps maintain the structural health of the knee joint, facilitating movement and stability.
Formation of the Genicular Anastomosis
The genicular anastomosis formed by the branches of the popliteal artery ensures that the knee joint is supplied with blood, even during movement, when certain arteries might be temporarily compressed. This anastomotic network allows for collateral circulation, meaning that blood can continue flowing to the knee through alternate pathways in case of arterial blockages or injury. The middle genicular artery, which directly penetrates the joint capsule, ensures that critical structures like the cruciate ligaments receive continuous blood flow.
Blood Supply to the Muscles of the Posterior Leg
In addition to supplying the knee, the popliteal artery also provides oxygenated blood to the muscles of the posterior leg. Through the sural arteries, the popliteal artery supplies the large muscles of the calf, including the gastrocnemius, soleus, and plantaris muscles. These muscles are involved in plantarflexion (pointing the foot downward), a movement that is critical for walking, running, and jumping. The popliteal artery’s blood supply to these muscles supports their function and ensures they receive the oxygen and nutrients necessary for normal contraction and movement.
Vascularization of the Popliteal Fossa
The popliteal artery also provides blood supply to the structures within the popliteal fossa, a diamond-shaped space located behind the knee. The artery ensures that the skin, connective tissues, and deeper structures within this region remain oxygenated and healthy. The artery’s branches also supply the surrounding tendons and ligaments that support the knee joint.
Termination and Blood Supply to the Lower Leg and Foot
At the lower border of the popliteus muscle, the popliteal artery terminates by splitting into the anterior tibial artery and posterior tibial artery:
- Anterior Tibial Artery: This artery supplies blood to the anterior compartment of the leg, including muscles responsible for dorsiflexion of the foot and extension of the toes.
- Posterior Tibial Artery: This artery supplies the posterior compartment of the leg and eventually delivers blood to the plantar surface of the foot through its branches (medial and lateral plantar arteries).
By terminating in these two arteries, the popliteal artery plays a critical role in supplying oxygenated blood to both the anterior and posterior compartments of the leg, as well as to the foot.
Oxygenation of Knee Ligaments and Cruciate Ligaments
The middle genicular artery, one of the smaller branches of the popliteal artery, penetrates the posterior aspect of the knee joint capsule to supply the cruciate ligaments (anterior and posterior) and the menisci. These structures are vital for stabilizing the knee and allowing for smooth joint movement. The blood supply from the popliteal artery ensures that these important ligaments receive adequate oxygenation and nutrients, enabling proper joint function and repair after minor injuries or strain.
Support for Dynamic Movements of the Knee
By providing blood to the muscles, tendons, ligaments, and other structures surrounding the knee joint, the popliteal artery ensures that the knee can perform its dynamic functions, such as flexion, extension, and rotation. These movements are crucial for walking, running, squatting, and other weight-bearing activities. The continuous supply of oxygenated blood helps prevent fatigue and injury to the muscles and tissues involved in these motions.
Collateral Circulation and Protection During Knee Flexion
The popliteal artery is vital for maintaining blood flow to the lower limb, especially during knee flexion, when other arteries may be compressed. Through the genicular anastomosis and collateral circulation, the popliteal artery helps ensure that blood can still reach the knee and leg, even when the artery is temporarily compressed by the flexion of the knee joint. This adaptive function protects the structures of the leg from ischemia during physical activity.
Clinical Significance
The popliteal artery is critically important due to its role in supplying blood to the knee, lower leg, and foot. Clinically, it is a common site for arterial diseases such as popliteal artery aneurysms, which are the most common peripheral arterial aneurysms and can lead to thromboembolism or rupture if untreated. Popliteal artery entrapment syndrome is another condition where abnormal positioning of muscles compresses the artery, causing leg pain during exertion.
In cases of peripheral artery disease (PAD), the popliteal artery may become narrowed or blocked, leading to reduced blood flow to the leg and foot, potentially resulting in ischemia, pain, or even tissue loss. The popliteal artery is also crucial during vascular surgeries and reconstructive procedures, where restoring blood flow to the lower limb is necessary. Palpation of the popliteal pulse can help assess circulation in the lower extremities, and it serves as a key site for bypass grafting when addressing occlusive arterial diseases.
