Fat Pad (Hoffa's) Impingement: Pain Below the Kneecap

What is the fat pad?

The infrapatellar fat pad, also called Hoffa's fat pad, is a soft, well-supplied cushion of fat that fills the space between the lower kneecap, the patellar tendon and the front of the shin bone. It helps the knee move smoothly and is one of the most sensitive structures in the joint, because it is rich in nerve endings.

When the fat pad is repeatedly pinched between the thigh bone and the kneecap, or bruised by a direct blow, it becomes swollen and inflamed. A swollen fat pad is pinched even more easily, so the problem can keep itself going until the cycle is broken.

Symptoms, in patients' own words

• "It hurts just under my kneecap, on either side of the tendon"
• "The pain is worse when I lock my knee straight or stand for a long time"
• "It looks puffy below the kneecap"
• "Walking in heels or going down stairs makes it worse"
• "It aches after kicking or after I hyperextend my knee"

Pain is usually felt at the front, below the kneecap, rather than deep inside the joint. Some people notice a tender, soft swelling either side of the patellar tendon.

Causes and who gets it

Fat pad impingement is common in people whose knees bend backwards slightly (hyperextension), which pinches the pad each time the knee locks out. It is seen in footballers, dancers, gymnasts, runners and gym users, and in people who stand for long shifts with their knees pushed back. A direct fall onto the front of the knee, or a sudden hyperextension injury, can start it.

It can also follow knee surgery, particularly arthroscopy or ACL reconstruction, where scarring of the fat pad causes stiffness and front-of-knee pain. Weak thigh and hip muscles, kneecap tracking problems and arthritis may contribute.

How it is diagnosed

Diagnosis relies mainly on the story and examination. Pressing on the fat pad while straightening the knee often reproduces the pain. Dr. Gelber also checks the patellar tendon, the kneecap joint and the meniscus, because these cause similar symptoms and can coexist.

An MRI is helpful when the diagnosis is unclear or pain persists. It can show swelling within the fat pad, scarring after surgery, or less common causes such as a cyst or a benign growth. Ultrasound can show swelling and guide an injection if one is needed.

Non-surgical treatment

• Avoid locking the knee straight: stand with a soft knee and shift weight between legs
• Taping to lift the lower kneecap and offload the pad, often effective in the short term
• Ice and a short course of anti-inflammatory medicine if suitable for you
• Physiotherapy to strengthen the quadriceps, hamstrings and hips and to control hyperextension
• A temporary change in training, such as reducing deep squats, kicking and downhill running
• Footwear with a small heel lift for some patients

Most patients improve over several weeks to a few months. If pain remains, an ultrasound-guided steroid injection into the fat pad may calm the inflammation and allow rehabilitation to progress.

When surgery is considered

Surgery is needed only in a small number of patients whose symptoms persist despite a full course of treatment, or who have scarring of the fat pad after previous surgery. Through knee arthroscopy, the inflamed or scarred portion of the fat pad is carefully trimmed and any associated problem is treated. Rehabilitation afterwards focuses on regaining full straightening and quadriceps strength, usually over a few weeks.

When to see a knee specialist in Doha

Book an assessment if pain below the kneecap lasts more than a few weeks, keeps you from training or work, follows a knee operation, or comes with marked swelling. Seek urgent care if the knee becomes hot, red and very swollen with fever. At Aman Hospital, Dr. Gelber examines the whole knee, reviews any scans you bring, and plans treatment around your sport, work and daily routine in Qatar.