Glossary
Hoffa's fat pad (infrapatellar fat pad)
Quick answer
Hoffa's fat pad, or the infrapatellar fat pad, is a soft cushion of fat that sits behind the patellar tendon, just below the kneecap. It is rich in nerves and blood vessels, so when it is pinched or inflamed it can be a surprisingly painful source of front knee pain, explains Dr. Pablo Gelber, knee surgeon at Aman Hospital in Doha.
What it is
The fat pad fills the space between the patellar tendon, the bottom of the kneecap and the front of the tibia, inside the capsule but outside the synovial lining. It changes shape as the knee moves, cushioning the tendon and helping spread joint fluid. It is one of the most sensitive tissues in the knee.
Why it matters for patients
Fat pad impingement happens when the pad is squeezed between the kneecap and the femur, typically when the knee is pushed fully straight or bent backwards. It can follow a direct blow, repeated hyperextension, for example in dance, gymnastics or some football actions, or swelling after arthroscopy or ACL surgery. People describe pain and puffiness on either side of the patellar tendon, worse when standing with the knees locked back, on prolonged standing or walking in heeled shoes.
Most cases settle with avoiding hyperextension, taping to unload the pad, strengthening and time; an injection is occasionally used. Surgery to trim the fat pad is reserved for persistent cases.
How it is examined
A surgeon presses either side of the patellar tendon and checks whether forcing the knee straight reproduces the pain. MRI may show swelling of the pad.
Frequently asked questions
Is fat pad pain related to body fat?
No. The fat pad is a normal structure in everyone's knee, regardless of body weight, and its problems come from pinching or irritation, not from weight gain.
Why does my knee hurt below the kneecap when I stand for a long time?
Standing with the knees locked back can squeeze the fat pad. Patellar tendinopathy and kneecap cartilage problems are other common causes, so an examination helps.
Related
