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Infrapatellar fat pad

The infrapatellar fat pad, also known as Hoffa’s fat pad, is a large, intracapsular but extrasynovial structure located in the anterior knee joint. It is made of fatty tissue and highly vascularized, occupying the space between the patella, femoral condyles, tibia, and patellar tendon.

It plays a role in shock absorption, joint lubrication, and stabilization of the knee during motion. Due to its rich innervation and vascularity, it is a common source of anterior knee pain in conditions such as Hoffa’s disease, impingement, fibrosis, and postsurgical scarring.

Synonyms

  • Hoffa’s fat pad

  • Infrapatellar adipose tissue

  • Anterior knee fat pad

Location and Structure

  • Location: Lies posterior to the patellar tendon, anterior to the femoral condyles and tibial plateau, and inferior to the patella

  • Structure: Consists of lobulated fatty tissue encased in fibrous septa, richly supplied with blood vessels and nerves

Relations

  • Anteriorly: Patellar tendon and retropatellar skin

  • Posteriorly: Femoral condyles, tibial plateau, anterior horns of menisci, and synovium

  • Superiorly: Inferior pole of patella and anterior joint capsule

  • Inferiorly: Tibial tuberosity and anterior tibial periosteum

  • Laterally/medially: Bound by medial and lateral patellar retinacula

Nerve Supply

  • Innervated by branches of the femoral nerve and saphenous nerve, making it highly sensitive to injury or inflammation

Arterial Supply

  • Supplied by branches of the genicular arteries (superior and inferior medial/lateral genicular branches from the popliteal artery)

Venous Drainage

  • Drains into the genicular venous plexus, then into the popliteal vein

Function

  • Acts as a shock absorber during knee flexion and extension

  • Facilitates smooth gliding of the patella and patellar tendon over the femoral condyles

  • Provides space compensation during knee movement

  • Rich innervation contributes to joint proprioception and nociception

  • Protects intra-articular structures from excessive shear forces

Clinical Significance

  • Hoffa’s disease: Painful impingement and inflammation of the fat pad between femur and patella

  • Postsurgical scarring or fibrosis: Common after ACL reconstruction or arthroscopy

  • Trauma: Contusions and hemorrhage may cause swelling and chronic pain

  • Tumors: Rare but can occur (lipoma, hemangioma, synovial tumors)

  • Appears enlarged, hyperintense, or heterogeneous on MRI when inflamed or fibrotic

MRI Appearance

T1-weighted images:

  • Fat pad shows high signal intensity (bright), similar to subcutaneous fat

  • Areas of fibrosis, hemorrhage, or scarring appear as low-signal foci

T2-weighted images:

  • Fat pad normally high signal intensity

  • Pathology (edema, inflammation, hemorrhage, fibrosis) appears as low or mixed signal intensity

STIR (Short Tau Inversion Recovery):

  • Normal fat pad is dark due to fat suppression

  • Pathology (edema, inflammation) appears bright hyperintense against suppressed background

Proton Density Fat-Saturated (PD FS):

  • Normal fat pad suppressed, appears dark

  • Abnormalities (edema, impingement, fibrosis) appear as bright signal areas

T1 Fat-Sat Post-Contrast:

  • Normal fat pad shows minimal or no enhancement

  • Inflamed or vascularized lesions (Hoffa’s disease, tumors) show heterogeneous or nodular enhancement

CT Appearance

Non-Contrast CT:

  • Appears as low-density fat tissue between patellar tendon and femur/tibia

  • Fibrosis or calcification may appear as soft tissue thickening or hyperdense foci

Post-Contrast CT:

  • Normal fat pad shows no significant enhancement

  • Pathologic lesions (tumors, inflammation, fibrosis) may enhance heterogeneously

  • Fat stranding indicates edema or inflammatory changes

MRI image

Infrapatellar fat pad (Hoffa’s fat pad) sagittal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI image

infrapatellar fat pad,(Hoffa's fat ) anatomy image

MRI image

infrapatellar fat pad,(Hoffa's fat )

CT image

Infrapatellar fat pad (Hoffa’s fat pad) axial ct

CT image

Infrapatellar fat pad (Hoffa’s fat pad) sag ct image