Joints and ligaments · Lower limb
Infrapatellar fat pad !
The infrapatellar fat pad is a soft cushion of fat behind the patellar tendon, below the kneecap; it can become painful when pinched.
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What it is
A soft cushion of fat behind the patellar tendon (Hoffa's fat pad).
What it does
Cushions the front of the joint; it can be irritated or pinched.
Key facts
- Where
- Behind patellar ligament, below patella; intracapsular but extrasynovial (Hoffa fat pad)
- Attaches
- Infrapatellar synovial fold to intercondylar fossa; alar folds at its sides
- Function
- Cushions front of knee and fills spaces during movement; richly innervated, a source of anterior knee pain
Relations
- In front
- Patellar ligament, which it cushions from behind
- Behind
- Joint cavity: femoral condyles and intercondylar notch, anterior horns of the medial and lateral menisci and the transverse (intermeniscal) ligament
- Above
- Lower pole of the patella
- Below
- Deep infrapatellar bursa and the upper tibia just above the tibial tuberosity
How to find it
With the knee straight and the quadriceps relaxed, the pad bulges as soft fullness on both sides of the patellar ligament just below the patella. In Hoffa syndrome this area is tender, and pressing it hurts more as the knee straightens.
Examination
- Hoffa test: the examiner presses both thumbs on either side of the patellar ligament with the knee bent, then the knee is extended; pain points to fat pad irritation
On imaging
On a lateral radiograph it is the triangular fat-density area behind the patellar ligament. On MRI it is bright on T1 like other fat; oedema, scarring and nodular lesions show against it, best on fat-suppressed sequences.
Clinical notes
- Hoffa syndrome: the pad is pinched between femur and tibia in forced extension, after a direct blow or in knees that hyperextend
- Anterior arthroscopy portals pass through it; a bulky pad can block the view and is partly trimmed
- Infrapatellar contracture after surgery or trauma: a stiff, scarred pad limits movement and lowers the patella
Test yourself
Think of the answer, then tap the question to see it.
Where does the infrapatellar (Hoffa) fat pad lie in relation to the knee capsule and synovium?
Behind the patellar ligament, below the patella: inside the fibrous capsule but outside the synovial cavity.
What is Hoffa syndrome, and when is the pain worst?
Pinching or inflammation of the richly innervated infrapatellar fat pad, giving anterior knee pain that is worst at full extension.
How can scarring of the infrapatellar fat pad after knee surgery change the patella?
It can shorten the patellar ligament and pull the patella low (patella baja).
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- corpus adiposum infrapatellare TA2 1908
- Official Spanish (DeCS)
- Cuerpo adiposo infrarrotuliano
- English (TA2)
- Infrapatellar fat pad
- Also called
- corpus adiposum genus · fat pad of Hoffa
Related
Sources: Terminologia Anatomica (TA2); Anatomy, Bony Pelvis and Lower Limb, Knee.
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Representative model, for educational purposes only.
