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The popliteus muscle is a small but vital muscle in the back of the knee, often referred to as the key to the knee. It is a deep muscle of the knee joint, forming the floor of the popliteal fossa. The popliteus muscle originates from the femur and the posterior horn of the lateral meniscus, and inserts onto the tibia. The popliteus tendon runs beneath the lateral collateral ligament and tendon of biceps femoris. The muscle assists in knee flexion and is involved in both the closed chain phase and open-chain phase of the gait cycle.
| Characteristics | Values |
|---|---|
| Shape | Small, thin, flat, triangular |
| Muscle Type | musclotendinous complex |
| Location | Knee joint, posterior aspect of the knee |
| Function | Knee flexion, stabilisation of the knee joint, medial and lateral rotation of the knee |
| Attachments | Femur, lateral meniscus, tibia |
| Nerve Supply | Tibial nerve (L4-S1), a branch of the sciatic nerve |
| Blood Supply | Branches of the popliteal artery |
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What You'll Learn
The popliteus muscle originates at the femur.
The popliteus muscle is a small but vital muscle in the back of the knee, often referred to as the "key to the knee". It is one of the main stabilisers of the knee joint, causing both medial and lateral rotation of the knee, and is involved in both the closed chain phase and open-chain phase of the gait cycle. The muscle is located in the deep posterior compartment of the leg, near the lateral femoral condyle.
The popliteus muscle originates at the femur, specifically from the lateral condyle of the femur by a strong tendon called the popliteus tendon. The popliteus tendon courses in the groove for the popliteus muscle on the lateral aspect of the lateral femoral condyle. This tendon is joined medially by tendinous fibres arising from the posterior horn of the lateral meniscus. The popliteus tendon then expands into a triangular muscle belly that passes inferomedially over the posterior joint capsule of the knee joint.
The popliteus muscle is intra-capsular but extra-articular and extra-synovial. It is innervated by the tibial nerve, from spinal nerve roots L4 through S1, with approximately 2 to 3 parallel tibial nerve branches. The entry point of the nerve is the lateral distal margin of the muscle, which is found inferior to the fibular head, and then splits into anterior, medial, and lateral distributions throughout the muscle. The popliteus muscle receives arterial blood supply mainly from branches of the popliteal artery, namely the inferior medial and lateral genicular arteries.
The popliteus tendon runs beneath the lateral collateral ligament and the tendon of the biceps femoris. The popliteal bursa, which is usually an extension of the synovial membrane, separates it from the lateral femoral condyle. The popliteus muscle assists in knee flexion and its function is decided according to the position of the lower extremity, i.e. weight-bearing or non-weight-bearing. In a non-weight-bearing position, the popliteus muscle is a primary internal rotator of the tibia.
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The muscle inserts on the tibia.
The popliteus muscle is a small, thin, flat, triangular-shaped muscle in the back of the knee. It is a deep muscle of the knee joint, forming the floor of the popliteus fossa. It is also known as the key to the knee as it is responsible for unlocking the knee when the leg is in an extended position. The muscle is located in the deep posterior compartment of the leg, near the lateral femoral condyle.
The muscle fibres originate from the lateral condyle of the femur and the posterior horn of the lateral meniscus, via a strong tendon called the popliteus tendon. From there, it runs diagonally across the posterior upper tibia and a portion of the joint capsule, to lie as the deepest muscle of the posterior knee region. The popliteus tendon passes beneath the lateral collateral ligament (LCL) and the tendon of the biceps femoris.
The popliteus muscle inserts on the tibia just proximal to the soleal line but below the tibial condyles. It inserts on the posterior surface of the tibia, above the soleal line. The soleus muscle originates just below the popliteus insertion point. The popliteus muscle is supplied by the tibial nerve, from spinal nerve roots L4 through S1, with approximately 2 to 3 parallel tibial nerve branches. The entry point of the nerve is the lateral distal margin of the muscle, which is found inferior to the fibular head, and then splits into anterior, medial, and lateral distributions throughout the muscle.
The popliteus muscle assists in knee flexion and its function is decided according to the position of the lower extremity, i.e. weight-bearing or non-weight-bearing. In open chain kinematics, it rotates the tibia medially, and in close chain kinematics, it laterally rotates the femur in the initial phase of knee flexion. The muscle is also involved in both the closed chain phase and open-chain phase of the gait cycle. During the closed chain phase, when the foot is in contact with the ground, the muscle externally rotates the femur on the tibia. In the open-chain phase or swing phase of the limb, the popliteus muscle internally rotates the tibia on the femur.
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It is a small but vital muscle
The popliteus muscle is a small but vital muscle in the back of the knee. It is triangular in shape and is located deep in the popliteal fossa, forming its floor. It is the only muscle in the posterior compartment of the lower leg that acts on the knee and not the ankle.
The popliteus muscle is responsible for unlocking the knee when the leg is in an extended position. It does this by laterally rotating the femur on the tibia. This function is important for walking and running, as it enables fluid movement. The muscle is also involved in the closed chain and open-chain phases of the gait cycle. During the closed-chain phase, when the foot is in contact with the ground, the popliteus muscle externally rotates the femur on the tibia. In the open-chain phase, or swing phase, when the limb is not in contact with the ground, the muscle internally rotates the tibia on the femur.
In addition to its role in the gait cycle, the popliteus muscle is the main stabiliser of the posterior knee region. It assists in knee flexion and helps to control tibial rotation during movement, which aids in the stability of the knee joint. The muscle is innervated by the tibial nerve and receives arterial blood supply from branches of the popliteal artery.
Injuries to the popliteus muscle are often caused by repetitive stress or direct blows and can lead to instability. These injuries can be treated with manual therapy, acupuncture, functional exercise, dry needling, and sports physical therapy.
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It is involved in the gait cycle
The popliteus muscle, often referred to as the "key of the knee", is a small but important muscle located in the posterior aspect of the knee joint. It is responsible for "unlocking" the knee during leg extension, allowing for leg flexion. This function is crucial in the gait cycle, as it enables the leg to move forward during walking or running.
During the gait cycle, the popliteus muscle controls the internal and external rotation of the tibia. In the closed chain phase, when the foot is in contact with the ground, the popliteus muscle externally rotates the tibia, allowing the leg to bear weight and maintain stability. In the open-chain or swing phase, the popliteus muscle internally rotates the tibia, facilitating the forward movement of the leg.
The popliteus muscle is also involved in knee stability and plays a role in resisting excessive external tibial rotation. It helps to maintain the neutral tibial rotation and prevents injuries to the posterolateral corner of the knee. This stabilising function is particularly important during weight-bearing activities, such as walking or running, ensuring that the knee joint remains stable and aligned during the gait cycle.
The muscle fibres of the popliteus originate from the lateral condyle of the femur and insert on the posterior surface of the tibia, just proximal to the soleal line. Its function can vary depending on whether the lower extremity is in a weight-bearing or non-weight-bearing state. In a non-weight-bearing position, the popliteus muscle acts as the primary internal rotator of the tibia.
Overall, the popliteus muscle plays a crucial role in the gait cycle by enabling leg extension and flexion, controlling tibial rotation, and stabilising the knee joint. Its function during the gait cycle is essential for maintaining proper alignment, stability, and movement of the knee during walking and running.
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It is a knee stabiliser
The popliteus muscle is a small yet vital muscle in the back of the knee. It is a deep muscle of the knee joint, forming the floor of the popliteus fossa. It originates from the femur and the posterior horn of the lateral meniscus, and inserts on the proximal tibia. The muscle fibres originate from the lateral condyle of the femur and the posterior horn of the lateral meniscus, via a strong tendon called the popliteus tendon. The popliteus tendon then expands into a triangular muscle belly that passes inferomedially over the posterior joint capsule of the knee joint.
The popliteus muscle is often referred to as the "key to the knee" or the "key of the knee" because it is responsible for unlocking the knee when the leg is in an extended position. It assists in flexing the leg upon the thigh and is especially called into action at the beginning of the act of bending the knee. When the knee is fully extended, the femur slightly medially rotates on the tibia to lock the knee joint in place. The popliteus muscle unlocks the knee by laterally rotating the femur on the tibia.
The popliteus muscle plays a crucial role in knee stability and is an overlooked source of posterior knee pain. It is one of the main posterolateral stabilisers of the knee joint, causing both medial and lateral rotation of the knee, thereby being involved in both the closed chain phase and open-chain phase of the gait cycle. In open chain kinematics, it rotates the tibia medially. In close chain kinematics, it laterally rotates the femur in the initial phase of knee flexion.
The popliteus muscle is the main stabiliser of the posterior knee region. It is involved in the gait cycle by initiating the flexion of the fully extended ("locked") knee. It also works as a smaller stabilizer in regard to internal rotation anterior translation and varus force. The popliteus assists in knee flexion and its function is decided according to the position of the lower extremity, i.e. weight-bearing or non-weight-bearing, as it is a primary internal rotator of the tibia in a non-weight-bearing position.
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Frequently asked questions
The popliteus muscle originates from the lateral condyle of the femur and the posterior horn of the lateral meniscus, via the popliteus tendon. It then inserts onto the tibia, just proximal to the soleal line and just below the tibial condyles.
The popliteus muscle is responsible for unlocking the knee when the leg is in an extended position. It does this by laterally rotating the femur on the tibia. It also medially rotates the tibia on the femur.
The popliteus muscle is often referred to as the "key of the knee" or the "key to unlock the knee" because of its role in "unlocking" the knee.
The popliteus muscle is involved in both the closed chain phase and open-chain phase of the gait cycle. In the closed-chain phase, when the foot is in contact with the ground, the muscle externally rotates the femur on the tibia. In the open-chain phase, when the limb is not in contact with the ground, the popliteus muscle internally rotates the tibia on the femur.
The popliteus muscle is a major stabiliser of the knee joint. It aids in knee stability by controlling tibial rotation during movement.
