Maximus Gage
The popliteus muscle is a small but vital muscle in the back of the knee that is responsible for knee flexion and internal rotation, especially in non-weight-bearing positions. It is also the main stabiliser of the posterior knee region, providing forward stability and assisting in knee retraction. The popliteus tendon, which connects the popliteus muscle to the head of the fibula, is crucial for the stability of the knee by preventing anterior movement of the tibia. The popliteus muscle is assisted by the tibialis posterior, flexor digitorum longus, and flexor hallucis longus, which together form the deep posterior compartment of the leg.
| Characteristics | Values |
|---|---|
| Muscle fibres | Originate from the lateral condyle of the femur |
| Insert on the posterior surface of the tibia | |
| Fibres also originate from the styloid portion of the fibular head | |
| Runs diagonally across the posterior upper tibia | |
| Forms the floor of the popliteal fossa | |
| Involved in the closed chain and open-chain phases of the gait cycle | |
| Rotates the tibia inward | |
| Unlocks the knee | |
| Assists in knee flexion | |
| Involved in knee joint mechanics | |
| Aids knee stability | |
| Supplies blood to the popliteal artery | |
| Receives nervous supply from the tibial nerve | |
| Rarely, a small sesamoid bone called a cyamella can be seen embedded in the popliteal tendon | |
| Injury to the popliteus causes posterolateral rotatory instability of the knee |
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What You'll Learn
- The popliteus muscle is a major stabiliser of the knee
- It is involved in both the closed and open-chain phases of the gait cycle
- The muscle assists in knee flexion and internal rotation
- The popliteus tendon contributes to knee stability
- Popliteus injuries can cause posterolateral rotatory instability of the knee
The popliteus muscle is a major stabiliser of the knee
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 popliteal fossa. It is the only muscle in the posterior compartment of the lower leg that acts just on the knee and not on the ankle. The popliteus muscle is a major stabiliser of the knee, 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 popliteus muscle externally rotates the femur on the tibia, "unlocking" the knee joint at the beginning of knee flexion. This movement allows for the initiation of flexion in a fully extended or "locked" knee. In the open-chain phase, or swing phase, when the foot is above the ground, the popliteus muscle acts on its insertion to medially rotate the tibia on the femur, providing stability to the tibia during knee flexion.
The popliteus muscle is also connected to the lateral meniscus in the knee, drawing it posteriorly during knee flexion to prevent the meniscus from being crushed between the tibia and femur. This action is particularly important in the early stages of bending the knee, as the popliteus produces a slight inward rotation of the tibia, which is essential for initiating this movement. The popliteus tendon contributes to the stability of the knee by providing forward stabilisation and assisting in knee retraction. It can withstand substantial loads before failure, ensuring knee stability during periods of stress.
Injury to the popliteus muscle can cause posterolateral rotatory instability of the knee, resulting in pain in the posterior aspect of the knee and leading to instability. Rehabilitation and strengthening of the popliteus muscle are crucial for maintaining knee stability and function, requiring targeted exercises and attention to the broader kinetic chain relationships, including balance, proprioception, and interaction with surrounding muscles.
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It is involved in both the closed and open-chain phases of the gait cycle
The popliteus muscle is a small but vital muscle in the human body, contributing significantly to the gait cycle. Its primary function is to "unlock" the knee during leg extension, allowing for flexion to occur. This "unlocking" of the knee is essential for initiating movement and facilitating the gait cycle.
During the closed-chain phase of the gait cycle, when the foot is in contact with the ground, the tibia is laterally rotated on the femur, locking the knee joint. At this point, the popliteus muscle acts on its origin, laterally rotating the femur on the fixed tibia, thereby unlocking the knee. This action enables the transition from a static, weight-bearing position to a dynamic, ambulatory one.
In the open-chain (swing) phase of the gait cycle, the foot is above the ground, and the tibia is free to move. Here, the popliteus muscle acts on its insertion, medially rotating the tibia on the femur. This movement provides stability to the tibia during knee flexion, ensuring a smooth and controlled gait.
The popliteus muscle, despite its small size, is a major stabiliser of the knee joint. Its ability to control the internal and external rotation of the tibia during walking and running is crucial for maintaining balance and coordination. This muscle's role in the gait cycle highlights its importance in lower body biomechanics and overall ambulation.
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The muscle assists in knee flexion and internal rotation
The popliteus muscle is a small, thin, flat, triangular muscle located at the back of the knee. It is a deep muscle of the knee joint, forming the floor of the popliteal fossa. It is the only muscle in the posterior compartment of the lower leg that does not influence the ankle joint.
The popliteus muscle assists in knee flexion and internal rotation. It originates 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 inserts on the posterior surface of the tibia, above the soleal line.
During the closed-chain phase of the gait cycle, when the foot is in contact with the ground, the popliteus muscle externally rotates the femur on the tibia, "unlocking" the knee joint and allowing flexion to occur. In the open-chain phase, when the foot is above the ground, the popliteus muscle acts to internally rotate the tibia on the femur, providing stability to the tibia during knee flexion.
The popliteus muscle is a major stabiliser of the knee joint, playing a crucial role in knee joint mechanics and enabling fluid movements like walking and running. It is also involved in both the closed-chain and open-chain phases of the gait cycle.
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The popliteus tendon contributes to knee stability
The popliteus muscle is a small, thin, flat, triangular muscle in the back of the knee. It is a deep muscle of the knee joint, forming the floor of the popliteal fossa. It is the only muscle in the posterior compartment of the lower leg that acts just on the knee and not on the ankle.
The popliteus muscle is connected to the tibia and femur via the popliteus tendon. 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 plays an important role in initiating flexion of the fully extended ("locked") knee. It does this by laterally rotating the femur on the tibia, which unlocks the knee and allows flexion to occur. This movement is especially important at the beginning of the act of bending the knee, as it produces the slight inward rotation of the tibia, which is essential in the early stage of this movement.
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Popliteus injuries can cause posterolateral rotatory instability of the knee
The popliteus muscle is a small, thin, flat, triangular-shaped muscle in the lower leg. It is a deep muscle of the knee joint, forming the floor of the popliteal fossa. It is the main stabiliser of the posterior knee region, and it is involved in both the closed-chain phase and open-chain phase of the gait cycle. The popliteus muscle can produce two types of actions: lateral rotation of the femur or medial rotation of the tibia.
Injuries to the posterolateral corner of the knee can be visualised using MRI, which can aid in diagnosing posterolateral rotatory instability. The Garrick test can also assist in assessing the popliteus muscle as the cause of lateral knee pain. This test involves the patient lying supine with hips and knees flexed to 90 degrees, followed by resisted internal rotation and passive external rotation of the knee. If pain is elicited, it suggests popliteal etiology.
Reconstruction of the posterolateral structures is often performed in acute settings or for symptomatic patients with chronic posterolateral rotatory instability. The popliteus tendon is commonly involved in reconstructive procedures, with repair techniques varying widely. In some cases, the popliteus tendon may be released to improve external rotational laxity in the late phase of knee flexion.
Overall, popliteus injuries can lead to posterolateral rotatory instability of the knee due to the crucial role of the popliteus muscle and tendon in stabilising the posterolateral corner of the knee joint.
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Frequently asked questions
The popliteus is a small, thin, flat, triangular muscle in the back of the knee. It is a deep muscle of the knee joint, forming the floor of the popliteal fossa.
The popliteus muscle is a major stabilising muscle of the knee. It is involved in both the closed chain phase and open-chain phase of the gait cycle. It also assists in knee flexion and internal rotation, especially in non-weight-bearing positions.
The popliteus muscle originates from the lateral condyle of the femur by a strong tendon called the popliteus tendon. It inserts on the posterior surface of the tibia, superior to the soleal line.
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