It hurts under my kneecap when I straighten my leg fully. Why?

Why straightening hurts

Hoffa's fat pad is a soft, sensitive cushion that sits behind and just below the kneecap, beneath the patellar tendon. As the knee straightens fully, the space at the front of the joint narrows. If the fat pad is swollen or the knee pushes into hyperextension, the pad gets squeezed between the kneecap, thigh bone and shin bone.

The fat pad has many nerve endings, so even mild irritation can be surprisingly painful.

What it typically feels like

• Ache or sharp pain just below the kneecap, often on both sides of the tendon
• Worse standing with the knee locked back, kicking, or walking in heels
• A puffy, soft swelling below the kneecap
• Pain on pressing either side of the tendon
• Often eased by standing with the knee slightly bent

What you can do now

Avoid standing with your knees braced straight; keep a soft bend. Reduce activities that snap the knee straight, such as kicking drills or straight-leg kickbacks in the gym, for a couple of weeks. Ice can calm a flare. Some physiotherapists use tape across the top of the kneecap to unload the fat pad.

Strengthening the thigh and hip muscles helps control the end of straightening, so the knee does not slam into it.

When to be seen in Doha

Book an assessment if the pain lasts more than a few weeks, keeps returning, follows an injury, or comes with locking or a large swelling. Other causes at the front of the knee, such as patellar tendinopathy, a meniscus problem or cartilage wear, can feel similar.

At Aman Hospital, Dr. Gelber examines the knee and arranges an MRI when needed, which can show fat pad swelling and rule out other problems.