Popliteus
Leg · Lower Limb
The popliteus is a small, flat, triangular muscle that forms the floor of the lower part of the popliteal fossa behind the knee. It arises from the lateral condyle of the femur and the lateral meniscus and passes downward and medially to insert on the posterior surface of the proximal tibia above the soleal line. Its distinctive role is to unlock the fully extended knee at the start of flexion: by laterally rotating the femur on the fixed tibia, it reverses the screw-home locking of the joint, and it also provides weak knee flexion. Its attachment to the lateral meniscus helps withdraw that cartilage during movement. It is supplied by the tibial nerve (L4, L5, S1).
Origin, Insertion, Action & Nerve
Origin
Lateral condyle of femur and lateral meniscus
Insertion
Posterior surface of proximal tibia (above soleal line)
Action
Unlocks knee (laterally rotates femur on fixed tibia); weak knee flexion
Nerve
Tibial nerve (L4, L5, S1)
Attachments explained
The Popliteus is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Lateral condyle of femur and lateral meniscus
Insertion
Posterior surface of proximal tibia (above soleal line)
Action & function
When the Popliteus contracts, it produces the following movements: Unlocks knee (laterally rotates femur on fixed tibia); weak knee flexion.
As part of the Leg group of the Lower Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Popliteus receives its nerve supply from the Tibial nerve (L4, L5, S1). This nerve carries fibres from spinal segment(s) L4, L5, S1.
Because a muscle can only contract when its nerve is intact, injury to the Tibial nerve or to its spinal roots (L4, L5, S1) can weaken or paralyse the Popliteus, impairing the movements it normally produces (unlocks knee (laterally rotates femur on fixed tibia)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Popliteus (the OIANS method)
Understand the popliteus through its unlocking function. A fully extended knee is locked by slight medial rotation of the femur on the tibia; the popliteus rotates the femur laterally to release this catch so flexion can begin. Because the tibia is normally fixed on the ground, thinking of the muscle as rotating the thigh outward on a planted leg makes its unusual action logical.
Fix its oblique course from the lateral femoral condyle down to the medial part of the posterior tibia, which crosses the back of the knee and explains why it also pulls on the lateral meniscus to protect it during flexion. Group it with the other tibial-nerve muscles of the leg, but note its distinctive roots (L4, L5, S1) and its unique job as the knee that unlocks the joint rather than moving the ankle.
Frequently asked questions
Where is the Popliteus located?
The Popliteus is a muscle of the Leg group, located in the Lower Limb.
What is the origin of the Popliteus?
Lateral condyle of femur and lateral meniscus
What is the insertion of the Popliteus?
Posterior surface of proximal tibia (above soleal line)
What movements does the Popliteus produce?
Unlocks knee (laterally rotates femur on fixed tibia); weak knee flexion
What nerve supplies the Popliteus?
Tibial nerve (L4, L5, S1)
Is the Popliteus free to study in OIANS?
The Popliteus is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Lower Limb is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
Study the Popliteus
Test yourself on Lower Limb muscles with interactive quizzes and flashcards in the free OIANS app.
Quiz yourself → Flashcards Open the OIANS app
Browsing is always free. A one-time Lifetime unlock adds every region's quizzes, flashcards, progress tracking and explore tools.