Patient question

My knee suddenly became stiff and swollen without an injury. What is happening?

Dr. Pablo GelberOrthopaedic Knee Surgeon

Quick answer

A knee that stiffens and swells within hours or a day without any injury is often a crystal flare such as gout or pseudogout, an arthritis flare, or occasionally a joint infection. A hot, red knee with fever is an emergency, warns Dr. Pablo Gelber, knee surgeon at Aman Hospital in Doha, Qatar.

Why the joint can swell on its own

The knee lining can become inflamed without any outside injury. Crystals forming in the joint fluid, an infection reaching the joint through the bloodstream, or an immune reaction can all trigger a rapid build-up of fluid. The swollen joint then feels tight and stiff, and you may not be able to bend or straighten it.

Because one of these causes, infection, can destroy cartilage quickly, a new hot, swollen knee should not be left to see if it settles.

Possible causes

Gout, from uric acid crystals, often after a large meal, dehydration or alcohol, and more common in men and with some blood pressure medicines
Pseudogout, from calcium crystals, more common in older adults
Septic arthritis, a bacterial infection of the joint, sometimes after a skin wound, injection or procedure
A flare of osteoarthritis after an unusually busy day
Inflammatory arthritis, sometimes the first sign of a wider condition
Reactive arthritis after a gut or urinary infection

Red flags: seek care the same day

Fever, shivers or feeling unwell
A hot, red knee that you cannot bear to move
Recent knee injection, surgery or a cut or infection on the leg
Diabetes, kidney disease, or medicines that lower immunity

Go to an emergency department in these cases. Drawing fluid from the knee and testing it is the way to rule infection in or out.

What to do and when to book

If there are no red flags, rest the knee, apply ice wrapped in a cloth, keep it elevated and drink plenty of water, especially in the Qatar heat where dehydration can trigger gout. Do not start or stop regular medicines without advice.

Book an assessment within a few days if the swelling has not clearly improved. At Aman Hospital in Doha, Dr. Gelber examines the knee, may draw off fluid to check for crystals and infection, and arranges blood tests and X-rays. Treatment then targets the cause.

Frequently asked questions

Can the heat in Qatar trigger gout in my knee?

Dehydration raises uric acid concentration and can trigger gout attacks, so drinking enough water in summer and during long working days outdoors helps.

Is it safe to have fluid drawn from the knee?

Yes, when done with sterile technique. It relieves pressure and gives the most useful information about the cause.

Will it keep happening?

Gout and pseudogout can recur. Once the cause is known, lifestyle changes and sometimes long-term medicine reduce further attacks.