Patient question
My knee gives way and then swells up. Is that serious?
Dr. Pablo GelberOrthopaedic Knee Surgeon
Quick answer
Swelling after a knee gives way means the episode irritated or injured something inside the joint, such as a torn ligament, meniscus or cartilage. A knee that repeatedly buckles and swells should be examined rather than played on, says Dr. Pablo Gelber, knee surgeon at Aman Hospital in Doha, Qatar.
What the swelling tells you
The knee lining reacts to damage by producing extra fluid. When swelling follows a giving-way episode, it is a sign that the shift was not harmless: joint surfaces or soft tissues were stressed enough to react.
The timing is useful. Swelling within an hour or two, with a tense, warm knee, often means bleeding into the joint from a torn ligament or a fracture. Swelling that builds overnight is more often fluid from irritation, as with a meniscus tear or cartilage injury.
Common causes
- An ACL tear, with repeated shifts damaging the meniscus and cartilage each time
- A meniscus tear that catches, makes the knee give and then swells the next day
- Kneecap instability, where each slip can bruise or chip the cartilage
- Arthritis flares, where buckling and swelling come together after a busy day
- A loose body moving inside the joint
What to do after each episode
Rest from sport, elevate the leg, use ice for 15 to 20 minutes a few times a day and a light compression sleeve. Keep gently bending and straightening the knee so it does not stiffen. Simple pain relief that suits you can help, following the packet or your pharmacist's advice.
Most importantly, do not return to football, padel or the gym until the cause is known. Repeated episodes are what turn a repairable injury into permanent cartilage damage.
Red flags and when to see a surgeon
- Seek urgent care for a hot, red knee with fever, a knee that cannot take weight, or one that locks and will not straighten
- Book a prompt assessment if swelling followed a twisting injury, or if this has happened more than once
At Aman Hospital in Doha, Dr. Gelber examines the knee, may draw off tense fluid when it helps, and usually arranges an MRI to look at the ligaments, meniscus and cartilage before advising on treatment.
Frequently asked questions
Should I have the fluid drained?
Usually it settles on its own. Drawing it off is considered when the knee is very tense and painful, or when infection or crystals need to be ruled out.
Does swelling mean I need surgery?
Not necessarily. It means the cause needs identifying. Some causes respond to physiotherapy; others, such as a displaced meniscus tear in a young knee, are better repaired early.
How long should the swelling last?
After a minor episode it usually eases within a few days to a couple of weeks. Swelling that persists or returns each time the knee gives way should be assessed.
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