Swollen Knee: Common Causes and What to Do
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A swollen knee is hard to miss. It feels tight and heavy, it does not want to bend all the way and it can look puffier than the other knee, especially around and above the kneecap. Sometimes the swelling appears within hours after a twist or a fall. Other times it builds up slowly over several days, without a clear reason.
Swelling is a sign that the knee is irritated. In many cases it settles with rest and simple care at home, but some causes need a doctor. Here is how to tell them apart.
How knee swelling develops
The knee joint normally contains a small amount of fluid that helps it move smoothly. When the joint is irritated, it can produce more fluid than usual. People sometimes call this "water on the knee". Swelling can also come from the soft tissues around the joint, for example from a small fluid-filled cushion in front of the kneecap or from a cyst at the back of the knee.
The most common causes
- Overuse. A long walk, a day of gardening or a sudden increase in activity can make the knee react with swelling, especially if it is already sensitive.
- Osteoarthritis. Worn cartilage can irritate the lining of the joint, which then produces extra fluid. The swelling often comes and goes in flare-ups.
- A twist or a knock. A twist, a fall or a knock can damage a ligament or a meniscus. Swelling that appears quickly, within a few hours, is a reason to have the knee checked.
- Bursitis. A small fluid-filled cushion in front of the kneecap can become irritated, for example after a lot of kneeling. It creates a soft, rounded bump.
- A cyst behind the knee. Extra fluid can collect at the back of the knee and cause tightness there. Read more in our article on pain behind the knee.
- Gout or other inflammatory conditions. These can make a knee suddenly hot, red, swollen and very painful.
What you can do at home
- Go easy on the knee for a few days. Cut back on what makes the swelling worse, such as long walks or kneeling, but keep moving the knee gently so it does not stiffen.
- Cool it. A wrapped cold pack for 10 to 15 minutes a few times a day can ease swelling. Our article on heat or cold for knee pain explains how to do this safely.
- Raise the leg. When you rest, lie down and support the leg so the knee is slightly above the level of your heart. This helps the fluid drain away.
- Gentle compression. A soft, well-fitting sleeve can give the knee a pleasant sense of support. It should feel snug, never tight, and deep marks on the skin are a sign that it is too small.
- Keep the muscles working. Simple exercises, like tightening the thigh muscle with the leg straight or slowly bending and straightening the knee in a comfortable range, help maintain strength without loading the joint.
When to see a doctor
- the knee swelled up quickly after a twist, a fall or a "pop"
- you cannot put weight on the leg or the knee gives way
- the knee is red and hot or you also have a fever (see a doctor the same day)
- the knee locks or you cannot straighten it
- your calf is also swollen, warm or painful
- the swelling does not go down after a few days of home care or keeps coming back
A swollen knee is the body's way of saying the joint needs attention. Most of the time, a few days of rest, cooling and keeping the leg raised help it settle. If the swelling is sudden, hot or keeps coming back, it is worth finding out why.
A sleeve you will actually wear
The best sleeve is the one that does not end up in a drawer. The KeenTrove Bamboo Knee Sleeve is made for exactly that:
- soft, breathable bamboo, comfortable even in summer
- fits snugly but does not dig in behind the knee
- does not lock the knee, so you move naturally
- wear it under your clothes during the day and in bed at night
With 60 days to get your money back, you have nothing to lose.
Note: this article is for information only and does not replace an examination by a doctor. If you have circulation problems or diabetes, or have recently had knee surgery, talk to your doctor before wearing compression.
