Infrapatellar fat pad

At a glance

English

Infrapatellar fat pad

Latin (TA2)

Corpus adiposum infrapatellare

System

Joint

Region

Lower limb

Side

Paired, left and right

About the infrapatellar fat pad

The infrapatellar fat pad, also called Hoffa's fat pad, is a soft mass of fatty tissue filling the space at the front of the knee between the patellar ligament, the lower pole of the patella, the front of the tibia and the femoral condyles. It lies inside the fibrous capsule but outside the synovial membrane, which it pushes backwards into the joint. In shape it is roughly a wedge or cylinder, thickest behind the patellar ligament and tapering towards its edges.

Above, the pad is attached to the lower pole of the patella; below, it is linked to the front of the tibia and the anterior horns of the menisci. From its deep surface the synovium is drawn back as the infrapatellar synovial fold, which reaches the intercondylar fossa of the femur, and on either side as the fringed alar folds. Small fat projections fill the gaps between the moving bones as the knee bends and straightens, changing shape as they go. Unlike most body fat, the pad is well supplied with nerves.

Its role is mainly mechanical. It acts as a soft filler and cushion that adapts its shape during movement, helps spread synovial fluid, protects the patellar ligament from rubbing on the tibia and may help support the patella. A small deep infrapatellar bursa separates the lower part of the ligament from the tibia nearby.

The pad can become a source of pain. After direct injury or repeated strain it may swell and be pinched between the kneecap and the femur when the knee straightens, giving sharp pain at the front of the knee; this is known as Hoffa syndrome. Surgeons sometimes trim it during arthroscopy to improve the view, but scarring can follow. In arthrofibrosis the pad may become fibrous and contract, pulling the kneecap lower than normal, a state called patella baja.

Attachments and function

Formed by

Attached above to the lower pole of the patella and the deep surface of the patellar ligament.

Joins

Attached below to the front of the tibia and the anterior horns of the menisci, and back by the infrapatellar fold to the intercondylar fossa.

Movements

Cushions and fills the front of the knee joint, changing shape during movement and protecting the patellar ligament.

Nerve supply

Branches of the femoral nerve and the genicular nerves; the pad is richly innervated and sensitive to pain.

Blood supply

The genicular arteries, chiefly the inferior medial and inferior lateral genicular branches of the popliteal artery.