Swollen Knee

If your knee is swollen and sore you can treat it with a combination of rest, ice packs and the right exercises. We guide you through the causes, symptoms, and the most effective ways to treat a swollen knee,including a number of simple exercises.

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Sanne-Maria Bjerno Medical Writer
Medically reviewed by 

Symptoms of a swollen knee
Causes of swollen knees
Pain relief
Recovery time
When to Contact a Doctor

Swollen and sore knees are very common. Both young and older people, active and non-active will very likely experience pain and swelling in the knee at some point in their lives. Often it’s hard to point to a specific explanation for the pain.

The knee joint is prone to injuries and swelling because it is one of the great weight bearers of the body. It absorbs shocks when you walk, run and jump. At the same time, the knee joint is not as stable as your hips and ankles. Therefore, strong muscles and ligaments play an important role in stabilising and securing balance.

The knee joint is where three large bones meet - the thigh bone (femur) and the two bones in your lower leg (the tibia and the fibula). The joint also consists of the kneecap, cartilage, joint linings, meniscus, ligaments and several bursae. Injury, overuse and disease can affect all these parts and lead to swollen knees.

In this guide, we tell you all you need to know about the causes, symptoms, and best ways to treat your swollen knee.

Looking for a solution to your swollen knee? Try the Injurymap exercise app now.

Symptoms of a swollen knee

The feeling of “water in the knee” is called knee effusion. It often occurs if the knee is injured or overused. It can also be caused by certain diseases, such as arthritis, bursitis or gout.

If your knee is swollen (effused) you may find it difficult or painful to completely bend or stretch it. It may also be uncomfortable or painful to put your weight on it. Sometimes the swelling reduces partially after some walking around, sometimes the pain gets worse during the day.

The swollen knee can be red and/or warm to the touch, but that’s not always the case. The look and feel of the knee depends on the underlying cause of the swelling. The knee may also change its shape, become bigger or grow bulges.

Causes of swollen knees

The most common causes of a swollen knee are easily treated and not causes for alarm.However, a swollen knee can also be a sign of an underlying issue that may need to be treated, either medically or surgically. Sometimes, it’s also relevant to change factors in your lifestyle.

Here are the six most common causes of a swollen knee:

1: Injury and overuse

Trauma to one or several of the parts in the knee can cause fluid or blood to run to the joint, resulting in swelling. The trauma doesn’t have to be a major one. It may be small or it may be the result of a long time’s overuse, making it difficult to say when or why exactly your knee started to swell.

Swelling as a result of an injury can occur as late as 36 hours after the injury happened.

If the swelling is a result of overload of the joint for a longer period of time you may need to take a look at your daily habits. Perhaps you need to lose weight, exercise differently, or choose shoes that absorb shock better.

2: Arthritis

Osteoarthritis and rheumatoid arthritis are the most common types of arthritis to cause swelling and pain in the knees. Osteoarthritis is the result of wear and tear over the years. It causes the cartilage between the bones to break down, making the knee joint stiff and painful.Rheumatoid arthritis is an autoimmune disease that causes the body’s own immune system to attack the joints. In this case, you will often experience pain in other joints as well. Septic arthritis and reactive arthritis may also be the cause behind your swollen knee, although these diseases are more rare than osteoarthritis and rheumatoid arthritis. Septic arthritis and reactive arthritis are caused by infections. This means they are not chronical like osteoarthritis and rheumatoid arthritis.

3: Bursitis

A swollen knee can be caused by an inflammation of one or more of the shock-absorbing bursae within the knee. The bursae are fluid-filled sacs that reduce friction in the joints. Non-septic bursitis often occurs after overuse. It can be painful, though that’s not always the case.Septic bursitis is caused by a microorganism and causes pus and fluid to gather within the knee, making it swollen and sore.

4: Gout and pseudogout

Gout is also called inflammatory arthritis. Gout occurs when small crystals of uric acid accumulate within the joint. The sharpness of the crystals cause stabbing pains and often the knee swells up, making the joint stiff and sometimes red.

Pseudogout has many of the same characteristics as gout, the main difference being the formation of calcium pyrophosphate crystals in the joint, and not uric acid crystals.

5: Baker’s cyst

Swelling in the back of the knee is most likely caused by a Baker's cyst, or popliteal cyst. The cyst typically forms after a longer period of swelling in the knee and the underlying cause is usually arthritis or a cartilage tear.

A Baker’s cyst is a fluid-filled cyst that causes an often visible or at least palpable bulge behind your knee. It is often accompanied by a feeling of tightness in the back of your knee that gets worse when walking around or trying to bend or stretch the knee.

6: Plica syndrome

About half the population has remnants of the development of the knee in the embryological phase. These remnants are called plicae and are shelf-like membranes within the knee joint.

If one or more of the plicae become inflamed and irritated it leads to swelling, pain, clicking, popping, and difficulties fully bending and stretching the knee. Often the syndrome gives you a sense of instability when walking upstairs, downstairs or on slopes.

Pain relief

  • Acute swelling and soreness of the knee joint should be treated with RICE - Rest, Ice, Compression, and Elevation. Ice packs on the joint can make the swelling go down and and reduce the pain. Try an ice pack (or a bag of frozen peas wrapped in a towel) for 15-20 minutes at the time, three to four times a day.
  • Pain medication can be helpful in the initial phase of the swelling if pain in the knee makes it hard for you to keep up with your daily routines. Pain medication such as NSAID (Ibuprofen) and paracetamol should have some effect on the pain. Ibuprofen also has an effect on any inflammation in the joint.
  • Resting the knee several times a day can relieve some of the discomfort and pain. But don’t rest too much, as it can weaken the muscles and make your pain even worse and make the joint prone to more injuries and pain in the future.


If you have no fever, visible bulges, or severe pain, exercising as much as the swelling and pain allows will likely speed up the healing process. Exercise increases the circulation in and around the joint, which has a positive effect on the body’s ability to heal itself.

Often a swollen knee needs time to recover, though, so make sure not to “push through the pain” too much. Turn down the intensity of your training while the knee is healing and take small breaks between the exercises. If working out makes the pain worse, make sure to give the knee some rest and turn down your exercise a little more.

Exercises for a swollen and sore knee

  1. Hamstring stretch
    30 sec. x 3 sets

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    Hamstring stretch

    and around your knee. Since the exercise does not involve putting weight on the knee joint, it is a good place to start.

    • Lie on your back.
    • Bend one leg and use both hands to grab your thigh.
    • Pull your thigh up against your chest, so that it's vertically over you.
    • Then, stretch the knee as much as possible.
    • You should feel a stretch in the back of your leg and knee.
    • Hold the position for 30 seconds and repeat 3 times on both legs.
  2. Two-legged hop
    5 reps x 2 sets

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    Two-legged hop

    When performing small, controlled jumps you strengthen small and large muscles in and around your knee joint. This also works to exercise the balancing function of the knee, as well as the whole leg.

    • Stand with your feet slightly apart.
    • Jump straight up and land with control on both legs by making sure that your knees go straight over your toes and do not collide with each other.
    • Perform 5 repetitions.
  3. Skiing exercise
    30 sec.

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    Skiing exercise

    This exercise strengthens the small and large muscles and ligaments in and around your knee, especially the thigh muscles. And it does so without applying the shocks of walking and running. It is therefore a gentle exercise that builds strength and increases circulation in the entire leg.

    • Stand up.
    • Bend one leg in the hip and knee so that the foot is clear of the floor.
    • Now swing your arms back and forth as if you are walking or cross-country skiing while at the same time performing small knee bends and knee stretches with the leg you are balancing on.
    • Repeat this for 30 seconds on each leg.
  4. Squat I
    10 reps x 3 sets

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    Squats strengthen the entire leg, including the important inner thigh muscles. The exercise also strengthens the lower back muscles and lower leg muscles. It’s important not to overdo this exercise, though, as it can overload the joint. Therefore, it is advised that you do the exercise partly, not going all the way up or down in the squat.

    • Stand up in front of a chair without touching it.
    • Stand on both legs with your feet slightly apart.
    • Your toes should point straight ahead.
    • Bend your knees slowly to a point where you almost touch the chair.
    • Then slowly go back up.
    • Perform 3 sets of 10 repetitions.

Recovery time

Swelling in the knee joint may last for several days. If the swelling does not go down within about a week, or the pain and/or swelling becomes worse, you should see your doctor about it.


Applying weight on an already strained or injured joint can be painful and seem counteractive. It is important, though, to not give up daily routines and activities. Inactivity can lead to one of the most common complications of swollen knees: muscle loss.

The knee is dependent on strong muscles and ligament to stabilise and balance the body during activities such as walking, running, and jumping. Strong muscles often prevent injuries and pain in the future, as they absorb shock as well as supporting the joint.

When to Contact a Doctor

If the swelling and pain in your knee does not subside by itself within about a week or two it may be a good idea to have your doctor take a look at it. Besides finding the cause of the swelling, your doctor can also help you manage the pain.

You should also contact your doctor, if:
  • Your knee is very painful or has changed shape
  • You can’t put any weight on your knee or it gives way when you try to walk
  • The knee joint completely locks or makes painful clicks
  • You have a fever, shivers and the knee is red.


If your knee is swollen and sore, you’re not alone. Most people will experience “water in the knee” and knee pain at some point in their lives.It is important to find out what causes the swelling. The correct treatment of the underlying cause is the best way to prevent swelling and pain in the future.

The most common causes are injury, overuse, arthritis, infection and inflammation.Rest is important, especially if the cause of the swelling is overuse. But exercise is even more important, as the increased blood circulation often helps heal the swelling. Furthermore, strong muscles prevent future pain and injuries.

The Injurymap app demonstrates a range of exercises that can help you treat and prevent swollen knees. The exercises can be done from the comfort of your own home with little to no equipment needed. . Download the app today and get back to living your life with a pain-free knee.

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About the author

Sanne-Maria Bjerno has 10 years’ experience writing about health, medicine, and treatment. She is a trained journalist originally educated at Medicine Today Denmark and has since worked for the largest Danish public hospital, Rigshospitalet, the doctors’ union and the physiotherapists’ union. Her passion for creating useful, evidence-based information aimed at broad audiences has given her a comprehensive knowledge about most types of health, treatment and medical research related subjects.