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# Suprapatellar bursa

The suprapatellar bursa is a fluid sac above the kneecap that is part of the knee joint space; it fills when the knee swells.

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## What it is

A fluid sac above the kneecap, connected to the joint.

## What it does

Lets the quadriceps tendon glide; it fills with fluid when the knee is swollen.

## Key points

- In most adults it opens widely into the knee joint and behaves as part of the joint cavity: effusion, blood or pus in the knee fills it
- Articularis genus pulls it up as the knee straightens, so it is not pinched between the quadriceps tendon and the [femur](https://durgical.com/en/anatomy/femur/)
- The usual window for ultrasound of a knee effusion and a classic site described for aspiration

## Key facts

**Where**
Between quadriceps tendon and femur, extending several cm above patella

**Attaches**
Held up by articularis genus muscle

**Function**
Communicates with knee joint cavity; lets quadriceps glide over femur; fills in knee effusion

## Relations

**In front**
[Quadriceps tendon](https://durgical.com/en/anatomy/tendon-of-quadriceps-femoris-muscle/), with the suprapatellar (quadriceps) fat pad between them at its lower end

**Behind**
Prefemoral fat pad and the front of the lower femoral shaft above the trochlea

**Above**
Articularis genus, attached to its upper end

**Below**
Opens into the knee joint above the [patella](https://durgical.com/en/anatomy/patella/) and the femoral trochlea

## How to find it

With the knee straight and relaxed, swelling above and on both sides of the patella that fills the normal hollows of the lower thigh marks a distended bursa. Pressing down from above the patella pushes this fluid under the kneecap, the first step of the patellar tap.

## Examination

- Patellar tap: the examiner's hand first presses fluid down out of the bursa, then pushes the patella back; a tap against the femur shows a moderate effusion

## On imaging

Lateral knee radiograph: an effusion makes a rounded soft-tissue density above the patella, pushing the quadriceps fat pad and the prefemoral fat pad apart. Ultrasound with the knee slightly bent and the probe along the quadriceps tendon shows small amounts of fluid, synovial thickening and loose bodies in the recess.

## Clinical notes

- Effusion, haemarthrosis and septic arthritis all distend it, so swelling above the kneecap is often the first visible sign of joint fluid
- Suprapatellar plica: a remnant of the fetal partition can thicken and catch during movement, causing anterior knee pain
- A wound just above the patella can enter the joint through the bursa; the suprapatellar approach for tibial nailing also passes through it

## Anatomical variants

- A suprapatellar plica (complete, partial or perforated) is found in many knees; a complete septum that cuts the bursa off from the joint is rare

## Development

It starts as a sac separate from the joint; the wall between them normally breaks down before birth, and what remains forms the suprapatellar plica or, rarely, a closed bursa.

## Test yourself

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

## Does the suprapatellar bursa communicate with the knee joint?

Yes, in most adults it opens widely into the knee and acts as part of the joint cavity, so effusion, blood or pus fill it.

## Which muscle holds up the suprapatellar bursa, and why?

The articularis genus pulls it up as the knee straightens, so it is not pinched between the quadriceps tendon and the femur.

## Between which structures does the suprapatellar bursa lie?

Between the quadriceps tendon in front and the femur behind, extending several centimetres above the patella.

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

## Its names

**Official Latin (TA2)**
bursa suprapatellaris TA2 2738

**Official Spanish (DeCS)**
Bolsa suprarrotuliana DeCS D002061

**English (TA2)**
Suprapatellar bursa

## Related

- [Rectus femoris tendon](https://durgical.com/en/anatomy/tendon-of-rectus-femoris/)
- [Joint capsule](https://durgical.com/en/anatomy/articular-capsule-of-knee-joint/)

Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=2094&filter=ths_termall&q=Bolsa%20Sinovial); [Anatomy, Skin Bursa](https://www.ncbi.nlm.nih.gov/books/NBK554438/); [Anatomy, Bony Pelvis and Lower Limb, Knee](https://www.ncbi.nlm.nih.gov/books/NBK500017/).

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