Patient question

My knee is swollen but I didn't injure it. Why?

Dr. Pablo GelberOrthopaedic Knee Surgeon

Quick answer

A knee that swells without any injury is usually reacting to something inside it: wear-related arthritis, a degenerative meniscus tear, crystals such as gout, inflammatory arthritis or, less often, infection. A hot, red knee with fever needs same-day care, explains Doha knee surgeon Dr. Pablo Gelber at Aman Hospital in Qatar.

Common reasons a knee swells on its own

Osteoarthritis: the most common cause after the age of about 45. The knee aches, feels stiff in the morning or after sitting, and swells after a busy day.
Degenerative meniscus tear: the meniscus can split with ordinary bending or getting up from the floor, so many people do not remember an injury. Swelling often follows a day of more activity.
Gout or pseudogout: crystals in the joint cause a sudden, very painful, warm swelling, often overnight. Dehydration in the Qatar summer, some medicines and certain foods can trigger gout.
Inflammatory arthritis: conditions such as rheumatoid or psoriatic arthritis can swell one or both knees, often with other joints, skin or back symptoms.
Bursitis: a soft swelling on the front of the kneecap rather than inside the joint, common with kneeling.
Infection: rare but serious, described below.

What you can do now

If the knee is not hot or red and you feel well, a few days of relative rest, ice for 15 to 20 minutes at a time, keeping the leg raised and gentle bending and straightening are reasonable. Drink enough water, especially in the heat. Simple pain relief that suits you may help.

Keep a note of when the swelling started, whether it came on over hours or weeks, and whether other joints are involved. That story helps the diagnosis more than most tests.

Red flags

The knee is hot, red and very painful and you have a fever, chills or feel unwell: possible joint infection, go to emergency the same day
You recently had a knee injection, surgery or a cut or wound near the knee and it is now swelling and painful
You have diabetes, take steroids or have a weakened immune system and the knee swelled suddenly
The calf is also swollen and tender, which can mean a clot
The knee locks or you cannot bear weight

When to see a knee surgeon in Doha

Book an assessment if the swelling has not settled within one to two weeks, keeps coming back, or limits walking, stairs or prayer. At Aman Hospital Dr. Gelber examines the knee, and an X-ray and sometimes an MRI or blood tests are arranged. If the cause is unclear, drawing off a little fluid with a needle and testing it can show crystals or infection. If an inflammatory arthritis is suspected, a referral to a rheumatologist is usually part of the plan.

Frequently asked questions

Can stress or heat alone make my knee swell?

Heat itself does not cause a knee effusion, but dehydration can trigger gout, and long hours standing in the heat can make an arthritic knee swell. Swelling of both legs and ankles is more often a circulation or heart issue than a knee problem.

Is a swollen knee without injury serious?

Usually it is a manageable problem such as arthritis or a meniscus tear, but it always has a cause. If it is hot and red with fever, treat it as urgent.