The popliteus muscle in the leg is used for unlocking the knees when walking, by laterally rotating the femur on the tibia during the closed chain portion of the

gait cycle A (bipedal) gait cycle is the time period or sequence of events or movements during locomotion in which one foot contacts the ground to when that same foot again contacts the ground, and involves propulsion of the centre of gravity In physics, ...

(one with the foot in contact with the ground). In open chain movements (when the involved limb is not in contact with the ground), the popliteus muscle medially rotates the tibia on the femur. It is also used when sitting down and standing up. It is the only muscle in the posterior (back) compartment of the lower leg that acts just on the knee and not on the ankle. The gastrocnemius muscle acts on both joints.

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 soleal line, also known as the popliteal line (in older texts), is a prominent ridge on the posterior surface of the tibia. It is the site of many muscle origins and insertions, such as those of popliteus muscle, soleus muscle, flexor digitoru ...

. 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 anatomy, a sesamoid bone () is a bone embedded within a tendon or a muscle. Its name is derived from the Arabic word for ' sesame seed', indicating the small size of most sesamoids. Often, these bones form in response to strain, or can be pres ...

in the lateral (outer) head of the gastrocnemius muscle. Rarely an additional inconstant muscle; the

popliteus minor The popliteus muscle in the leg is used for unlocking the knees when walking, by laterally rotating the femur on the tibia during the closed chain portion of the gait cycle (one with the foot in contact with the ground). In open chain movements ...

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 Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

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 The posterior compartment of the leg is one of the fascial compartments of the leg and is divided further into deep and superficial compartments. Structure Muscles Superficial posterior compartment Deep posterior compartment Blood ...

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

External links

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PTCentral
{{Authority control Calf muscles Muscles of the lower limb