Popliteus muscle

Structure

The popliteus muscle originates from the lateral surface of the lateral condyle of the femur by a rounded tendon. Its fibers pass downward and medially. It inserts onto the posterior surface of tibia, above the soleal line. The popliteus tendon runs beneath the lateral collateral ligament and tendon of biceps femoris. The muscle also runs above the lateral meniscus but has no connection with the meniscus in 45% of the cases, but has strong connection with it in 17.5% of the cases. Therefore, popliteus muscle is extrasynovial, extra-articular, and intracapsular.

Nerve supply

The popliteus muscle is supplied by the tibial nerve, from spinal roots L5 and S1.

Variation

There is sometimes an additional head from the sesamoid bone in the lateral (outer) head of the gastrocnemius muscle.

Rarely an additional inconstant muscle; the popliteus minor is seen. It originates from the femur on the inner side of the plantaris muscle and inserts into the posterior ligament of the knee-joint.

Peroneotibialis, 14% of population. Origin is inner side of the head of the fibula, insertion into the upper end of the oblique line of the tibia, it lies beneath the popliteus.

Another variant, the cyamella, is a small sesamoid bone embedded in the tendon of the popliteus muscle. It is rarely seen in humans, with prevalence rates from 0.57–1.8%, but has been described more often in other primates and certain other animals.

Function

The popliteus assists in flexing the leg upon the thigh; when the leg is flexed, it will rotate the tibia inward.

It is especially called into action at the beginning of the act of bending the knee, in as much as it produces the slight inward rotation of the tibia, which is essential in the early stage of this movement.

When the knee is in full extension, the femur slightly medially rotates on the tibia to lock the knee joint in place. Popliteus is often referred to as the "Key" to unlocking the knee since it begins knee flexion by laterally rotating the femur on the tibia.

Popliteus is also attached to the lateral meniscus in the knee and draws it posteriorly during knee flexion to prevent crushing the meniscus between the tibia and femur as the knee flexes.

Additional images

File:Popliteus large.gif|Animation File:Gray439-Musculus popliteus.png|Deep layer of muscles on the back of the right leg File:Sobo 1909 305.png|Muscles of deep posterior compartment of the right leg

Surgery

Injury to the Popliteus causes posterolateral rotatory instability of knee. This can be treated with Arthroscopic Popliteus Sling reconstruction using the popliteus portal.

References

References

1. (2017-01-01). "2 - Lateral and Posterior Knee Anatomy". Elsevier.
2. (March 2014). "Comprehensive Review of the Anatomy, Function, and Imaging of the Popliteus and Associated Pathologic Conditions". RadioGraphics.
3. [http://www.bartleby.com/107/pages/page485.html Gray, Henry. 1918. Anatomy of the Human Body. Page 485]
4. (July 2021). "Cyamella (a popliteal sesamoid bone) prevalence: A systematic review, meta-analysis, and proposed classification system". Clinical Anatomy.
5. (2006). "Popliteus muscle sesamoid bone (Cyamella): Appearance on radiographs, CT and MRI". Surgical and Radiologic Anatomy.
6. (March 2020). "Muscular architecture of the popliteus muscle and the basic science implications". The Knee.
7. Kodkani, Pranjal. (1 March 2011). "Arthroscopic Popliteus Sling Reconstruction—The ''Popliteus Portal''". Techniques in Knee Surgery.