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# Popliteus

The popliteus is a small muscle behind the knee that unlocks the straightened knee so it can start to bend.

Official name: Popliteus muscle

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## What it is

A small, flat muscle behind the knee.

## What it does

Unlocks the straight knee so it can start to bend.

## Key points

- Its tendon runs inside the knee capsule but outside the synovium, passing through a gap in the attachment of the lateral meniscus (the popliteal hiatus)
- Part of the posterolateral corner of the knee with the lateral collateral and popliteofibular ligaments; injury causes posterolateral rotatory instability
- Forms the lower part of the floor of the popliteal fossa; the popliteal artery divides into the anterior and posterior tibial arteries at its lower border
- The lateral meniscus is less firmly fixed to the capsule at the hiatus and is pulled back by popliteus, one reason it is more mobile than the [medial meniscus](https://durgical.com/en/anatomy/medial-meniscus/)

## Key facts

**Origin**
Lateral femoral condyle (popliteal groove); posterior horn of lateral meniscus

**Insertion**
Posterior tibia above soleal line

**Action**
Unlocks extended knee (laterally rotates [femur](https://durgical.com/en/anatomy/femur/) on fixed tibia); weak knee flexion; pulls lateral meniscus back

**Nerve**
Tibial nerve (L4–S1)

**Blood supply**
Inferior medial and lateral [genicular arteries](https://durgical.com/en/anatomy/superior-lateral-genicular-artery/) (from popliteal artery)

## Relations

**Course**
From its groove on the lateral femoral condyle the tendon runs deep to the lateral collateral ligament and through the popliteal hiatus behind the [lateral meniscus](https://durgical.com/en/anatomy/lateral-meniscus/), then fans out as a triangular belly down and medially to the [tibia](https://durgical.com/en/anatomy/tibia/) above the soleal line

**Superficial**
[Popliteal artery](https://durgical.com/en/anatomy/popliteal-artery/) and vein and the [tibial nerve](https://durgical.com/en/anatomy/tibial-nerve/), then [plantaris](https://durgical.com/en/anatomy/plantaris-muscle/) and the two heads of gastrocnemius

**Deep**
Back of the upper tibia, the proximal tibiofibular joint and the knee capsule

**Lateral**
Lateral collateral ligament, superficial to its tendon, and the lateral meniscus, linked to it by popliteomeniscal fascicles

**Below**
Soleal line and the [soleus](https://durgical.com/en/anatomy/soleus-muscle/) origin; the popliteal vessels and tibial nerve pass under the tendinous arch of soleus just below it

## How to find it

It cannot be felt. It is seen in the floor of the popliteal fossa in a posterior approach to the knee. On MRI its tendon sits in a groove on the lateral femoral condyle and runs behind the posterior horn of the lateral meniscus.

## Examination

- Dial test (prone, external rotation of both feet compared at 30° and 90° of knee flexion): more rotation on one side at 30° only suggests a posterolateral corner injury; at both angles, a combined posterolateral corner and [posterior cruciate ligament](https://durgical.com/en/anatomy/posterior-cruciate-ligament/) injury
- Posterolateral drawer test: with the foot externally rotated, a backward push makes the lateral tibial plateau rotate posteriorly, pointing to a posterolateral corner injury

## On imaging

On MRI the tendon sheath at the hiatus can mimic a tear of the posterior horn of the lateral meniscus, and a small sesamoid in the tendon (cyamella) can mimic a loose body or tear.

## Clinical notes

- Posterolateral corner injuries often accompany anterior or posterior cruciate ligament tears; missing them is a common cause of failed cruciate reconstruction
- Popliteus tendinopathy causes posterolateral knee pain, typically in downhill running
- The popliteal artery is held in place near the lower border of popliteus and at the soleal arch, which is why knee dislocations and upper tibial fractures can tear it

## Anatomical variants

- A sesamoid in its tendon (cyamella) is uncommon
- A small extra muscle, popliteus minor, is rare

## Development

A ventral (flexor) muscle mass derivative of the deep calf, supplied by a branch of the tibial nerve that curls round its lower border.

## Test yourself

Think of the answer, then tap the question to see it.

## What is the main action of the popliteus?

It unlocks the extended knee by laterally rotating the femur on the fixed tibia; it also pulls the lateral meniscus back.

## What is the popliteal hiatus?

The gap in the attachment of the lateral meniscus through which the popliteus tendon passes, inside the capsule but outside the synovium.

## Of which knee complex is the popliteus part, and what does its injury cause?

The posterolateral corner, with the lateral collateral and popliteofibular ligaments; injury causes posterolateral rotatory instability.

## What does more external rotation at 30° only, on the dial test, suggest?

A posterolateral corner injury; more rotation at both 30° and 90° suggests a combined posterolateral corner and posterior cruciate ligament injury.

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Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
musculus popliteus TA2 2665

**Official Spanish (DeCS)**
Músculo poplíteo

**English (TA2)**
Popliteus muscle

## Related

- [Tibial nerve](https://durgical.com/en/anatomy/tibial-nerve/)
- [Popliteal artery](https://durgical.com/en/anatomy/popliteal-artery/)
- [Popliteus tendon](https://durgical.com/en/anatomy/tendon-of-popliteus/)
- [Fibula](https://durgical.com/en/anatomy/fibula/)
- [Tibia](https://durgical.com/en/anatomy/tibia/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Bony Pelvis and Lower Limb: Popliteus Muscle](https://www.ncbi.nlm.nih.gov/books/NBK526084/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/popliteus-muscle/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/popliteus-muscle/