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Suprapatellar fat pad

The suprapatellar fat pad, also called the quadriceps fat pad, is an intracapsular but extrasynovial structure located in the anterior knee. It occupies the space between the quadriceps tendon and the suprapatellar recess of the knee joint. Along with the infrapatellar (Hoffa’s) fat pad and prefemoral fat pad, it forms part of the three main anterior knee fat pads.

It serves as a cushion during knee flexion and extension, prevents friction between the quadriceps tendon and the distal femur, and provides synovial support. This fat pad is clinically relevant because it can become inflamed, hypertrophied, or impinged, leading to anterior knee pain.

Synonyms

  • Quadriceps fat pad

  • Anterior suprapatellar fat pad

  • Superior knee fat pad

Location and Structure

  • Lies superior to the patella within the anterior knee joint

  • Occupies the space between the quadriceps tendon (anterior) and the suprapatellar recess/joint capsule (posterior)

  • Intracapsular but extrasynovial in nature

Relations

  • Anteriorly: Quadriceps tendon

  • Posteriorly: Suprapatellar recess of the knee joint and femur

  • Superiorly: Lower fibers of quadriceps femoris

  • Inferiorly: Upper margin of the patella and continuous with prefemoral fat pad

Nerve Supply

  • Supplied by sensory branches of the femoral nerve and articular branches around the anterior knee

Arterial Supply

  • Superior genicular arteries (from popliteal artery)

  • Contributions from descending branches of the lateral circumflex femoral artery

Venous Drainage

  • Follows arterial supply → popliteal vein and femoral vein tributaries

Function

  • Acts as a cushion and shock absorber for the quadriceps tendon during knee motion

  • Facilitates smooth gliding of the quadriceps tendon over the femur

  • Contributes to joint stability by filling potential space and supporting the synovium

  • Involved in inflammatory and impingement syndromes causing anterior knee pain

Clinical Significance

  • Suprapatellar fat pad impingement syndrome: hypertrophy and inflammation may cause mass effect and anterior knee pain

  • May be mistaken for synovitis, bursitis, or tumor on imaging

  • Can become inflamed in overuse syndromes, trauma, or degenerative joint disease

  • Hypertrophy or edema may cause restricted motion and anterior knee discomfort

MRI Appearance

T1-weighted images:

  • Fat pad appears homogeneously bright

  • Inflammation or fibrosis shows focal low signal intensity

T2-weighted images:

  • Normal fat pad appears intermediate to bright

  • Edema or inflammation: focal high signal areas within fat pad

STIR (Short Tau Inversion Recovery):

  • Normal fat suppressed to dark signal

  • Edema, inflammation, or impingement appear as bright hyperintense regions

Proton Density Fat-Saturated (PD FS):

  • Normal fat suppressed to dark signal

  • Pathological changes show bright signal intensity

T1 Fat-Sat Post-Contrast:

  • Normal fat pad shows no significant enhancement

  • Inflammation shows focal or diffuse enhancement

  • Impingement/fibrosis may show irregular enhancing areas

CT Appearance

Non-Contrast CT:

  • Fat pad appears as low-density structure (-80 to -120 HU)

  • Well-differentiated from adjacent soft tissues by surrounding capsule and tendon

Post-Contrast CT:

  • Fat pad does not enhance normally

  • Pathological changes (edema, tumor, inflammation) may show surrounding soft tissue enhancement or obscuration of margins

MRI image

Suprapatellar (quadriceps) fat pad sagittal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI image

Suprapatellar fat pad anatomy mri 3t image

MRI image

Suprapatellar fat pad

CT image

Suprapatellar (quadriceps) fat pad ct image

CT image

Suprapatellar (quadriceps) fat pad ct sag image