What Causes Knee To Swell Up

How To Care For A Swollen Knee

This blog post was updated for content on October 20. 2020. Existing comments have not been modified or removed.

Knee swelling occurs when excess fluid accumulates on or around the knee joints. Doctors call this an effusion, and some people call it water on the knee. Sometimes, swelling will go away with home treatments. Other times, it may require visiting a doctor for medical treatment.

Why You Should Get A Clear Knee Pain Diagnosis

At Wimbledon Clinics, we keep things scientific, which means we give you the right treatment from the start so you dont have to waste your precious time and money.

We do this by giving you a clear diagnosis and an assessment of the severity of the problem, which may include an MRI scan. Only then do we recommend the treatment options to help you get back to your best as soon as possible.

These may include rest, anti-inflammatory tablets and, on occasion, steroid injections.

For more significant injuries, such as those to ligaments, some form of knee support or knee brace may be required but this would normally only be fitted after a clear knee pain diagnosis has been made.

Our experienced orthotist can advise you on the best knee supports and knee braces to help you.

For people with osteoarthritic knees, treatment can include injections of hyaluronic acid or PRP .

These injections can reduce pain and knee swelling with improvements sometimes lasting up to a year.

Perhaps You’re Just On Your Feet A Lot But The Swelling Also Could Signal A Potentially Serious Condition

Anyone can experience swollen feet from time to time. It’s common especially after walking or standing for long periods and it’s often remedied by resting and elevating those tired dogs.

Sometimes, however, swelling is a red flag for a more serious underlying problem.

“My approach is to consider potential problems in each of the body’s systems, such as the heart and blood vessels, bones, and skin,” explains Dr. James Ioli, chief of podiatry services at Harvard-affiliated Brigham and Women’s Hospital and co-editor of the Harvard Special Health Report Healthy Feet .

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Rapid Knee Swelling After An Injury

A swollen knee that develops immediately after an injury, within minutes, is usually due to haemarthrosis, where blood accumulates in the joint. Essentially what happens is that a structure inside the knee gets damaged and starts to bleed, building up pressure in the joint.

Knee swelling after an injury is normally profuse and the knee balloons up. It will feel tense and very sore and is often accompanied by bruising, although that may take longer to develop.

There are three main injuries that cause a swollen knee from a haemarthrosis:

1. Ligament Tear:Where a knee ligament ruptures . This is the most common cause and usually involves the ACL . Other symptoms include instability and pain Learn More >

2. Meniscus Tear:A tear in the outer rim of the cartilage lining the knee. Associated symptoms include locking and pain on stairs and when squatting Learn More >

3. Bone Fracture: A break in one of the knee bones such as a patellar fracture. In most cases, it will be obvious if you have broken a bone Learn More >

A swollen knee caused by a haemarthrosis like these needs urgent medical attention.

Choose from the links or visit the Knee Injuries section to find out more about these common causes of knee swelling, including symptoms and treatment options.

Causes Of Knee Swelling

Trauma is a common cause of swelling in the knee. In these instances the fluid in the knee might be blood from a meniscus tear or an ACL tear. The swelling from an acute injury will diminish over time as the blood is reabsorbed. If you have a very swollen knee after a traumatic injury you should see an Orthopedic Surgeon to determine what type of injury you might have sustained. Most injuries that result in significant swelling due to bleeding have a ligament tear such as an ACL tear. Cartilage injuries are less common, but still on the list of possibilities.

The type of fluid in your knee can help us determine what is wrong with your knee. It is not uncommon for us to recommend putting a needle into your knee for a fluid sample. That sample can be tested to look for common sources of knee swelling. As youll see below just the appearance of the fluid can help us determine what is wrong.

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How Is Knee Swelling Treated

Depending on the type and severity of your problem, treatments range from surgery to home remedies. Non-surgical remedies include:

• RICE: an abbreviation for Rest, Ice, Compression and Elevation, is best to do shortly after suffering an injury. RICE can be helpful for managing minor pain.
• Compression: wrapping the knee not too tightly in an elastic bandage
• Physical therapy: doing exercises to strengthen the knee and improve its stability
• Wearing a brace on the knee
• Taking over-the-counter pain-relief medication
• If you are overweight, losing weight to reduce pressure on the knee

In some cases pain medication or a lubricating substance might be injected into the knee. Or a needle may be used to reduce swelling by removing excess fluid.

An Infection Could Be Lurking

Perhaps the most dire cause of knee swelling, infection in the knee joint warrants a hasty trip to the doctor. When an infection gets into the knee joint, the knee quickly becomes really swollen, red, and hot, says Dr. Gladstone. If untreated, infection can affect the whole body, causing fevers and body shakes.

Though a poorly-cleaned gash on the knee can lead to infection, infections elsewhere in the body can make their way through the bloodstream and into joints, Dr. Gladstone explains.

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What To Expect From Your Doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may leave time to go over points you want to discuss in depth. You may be asked:

• Have you injured your knee recently? If so, describe the injury in detail.
• Does your knee “lock” or feel unstable?
• Has your knee felt warm or looked red? Do you have a fever?
• Do you play recreational sports? If so, what sports?
• Do you have any type of arthritis?
• Do you have a family history of autoimmune disease?

© 1998-2019 Mayo Foundation for Medical Education and Research . All rights reserved.Terms of use.

Symptoms That Might Indicate A Serious Condition

In some cases, behind knee swelling can signal a serious condition that should be immediately evaluated in an emergency setting. Seek immediate medical care if you, or someone you are with, have any of these serious symptoms including:

• Coldness of the feet, with weak or absent pulses
• Difficulty breathing
• Loss of sensation in the lower leg
• Obvious breakage or deformity of the bones
• Paralysis
• Uncontrollable pain

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Or You May Have A Bakers Cyst

Also known as popliteal or synovial cysts, Bakers cysts are fluid-filled lumps that develop on the back of the knee. According to Dr. Gladstone, theyre pretty common and nothing to be too alarmed about.

Deep within the knee joint, theres a layer of thin tissue called the capsule between your bones, Dr. Gladstone explains. When some sort of damage causes swelling within the knee joint, the pressure pushes extra fluid in the capsule out behind the knee joint, essentially creating a what looks like a swollen ball at the back of the knee.

Not typically too painful, Bakers cysts are often caused by arthritis or an acute injury within the knee. In some cases, they disappear on their own, but often reoccur if you dont treat the underlying cause.

Not To Be Missed If You Have Pain Behind The Knee Or Back Of The Leg

• It is very important to note that pain at the back of your knee may be referred pain from your lower back. This referred pain would most likely be a poorly localized, dull ache, not related to knee movements, but aggravated by movements in your lower back So do be aware of that possibility

• Deep Vein Thrombosis may occur following surgery, a period of immobilization such as a long flight or time spent on extended bed rest, following an injury, in woman taking estrogen, or in obese patients. It may present as pain in the calf, or in the back of the knee. There may be some mild swelling, tenderness or skin discoloration. If you are worried you may have a DVT, speak to your doctor to arrange for further investigations such as a Doppler ultrasound.

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What To Expect At Your Office Visit

Your provider will perform a physical exam, and look at your knees, hips, legs, and other joints.

Your provider may do the following tests:

• MRI of the knee if a ligament or meniscus tear could be the cause
• CT scan of the knee
• Joint fluid culture

Your provider may inject a steroid into your knee to reduce pain and inflammation.

You may need to learn stretching and strengthening exercises. You also may need to see a podiatrist to be fitted for orthotics.

In some cases, you may need surgery.

Gradual Knee Swelling Without An Injury

A swollen knee that develops gradually is usual a sign of an underlying knee condition rather than an injury. The fluid on the knee tends to come and go and varies in amount. There is usually only mild to moderate amounts of swelling in these cases.

Arthritisis the most common cause of gradual knee swelling, often referred to as water on the knee. Arthritis is the wear and tear of the cartilage and bones. It causes the body to produce extra fluid in the knee, which fluctuates in amounts. Other symptoms of arthritis include stiffness and crepitus .

Sometimes if the leg has been overworked, or gets knocked or twisted, the joint gets irritated and responds by producing more fluid to try and protect and heal itself, hence the term water on the knee.

Visit the Arthritissection to find out more including causes, symptoms and treatment options.

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What Symptoms Are Related To Joint Pain And Swelling

The symptoms of joint pain and swelling can vary from person to person, and depend on which joints are affected. The pain and swelling is often accompanied by stiffness, aches and a feeling of heat or warmth.

In some cases, it can lead to problems moving around, completing daily activities , and for some people, working.

Joint pain and swelling may be better or worse at different times of the day. For example, you may find that your joint pain and swelling is worst first thing in the morning. Pain and swelling in the joints can also lead to tiredness and fatigue.

What Are The Most Common Causes Of Joint Effusion

There are several reasons why your knee or other joints might swell with fluid. The most common reasons include:

• Infection. An infection in your joint is called septic arthritis. Septic arthritis is a serious disease that can damage or even destroy your joint. You might need a joint replacement a type of surgery because of it. When you have an infection, your joint tissues can fill with pus. Pus is a protein-rich liquid thats full of dead white blood cells.

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Bursitis Could Be To Blame

Often confused with arthritis, bursitis is another condition that can cause swollen knees. Bursitis is a reaction in which sacks of fluids, blood vessels, and nerve endings that cushion your jointscalled bursaebecome inflamed, explains Dr. Gladstone. Typically, bursitis occurs across the front of the knees as a result of excess pressure and friction on the joint over time.

Those little blood vessels bleed and the bursa produces excess fluid, which creates this giant, swollen pouchlike a bubble of fluid just below the skin, Dr. Gladstone says. These inflamed pouches, which can take on all sorts of shapes and sizes, can be incredibly painful to put pressure on.

Bursitis is most common in people who work a lot on their knees, like carpenters, plumbers, and tile-setters, says Dr. Gladstone. However, a good fall can cause bursitis, too.

Nighttime Knee Pain In Adolescents

Many teenagers and adolescents suffer from a condition thats called anterior knee pain. This causes pain in the front or center of the knee and can often be worse at night.

Doctors from the American Academy of Orthopedic Surgeons describe this type of knee pain as dull and achy. The pain may come on gradually, and physical activity can make the knee pain worse. The other symptoms of adolescent anterior knee pain include:15

• Popping noises in the knee when climbing stairs
• Nighttime knee pain
• Pain when bending the knee
• knee pain during intense physical activity

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Should I Avoid Solanine

The nightshade family of vegetables includes tomatoes, potatoes, and peppers. These contain the chemical solanine. Some people believe this chemical can cause arthritis pain, but no studies or research have ever shown this claim to be true.

A person with OA needs to maintain a healthy weight, because excess weight puts additional strain on the joints. This means more pain, inflammation, and swelling.

Here are some tips to help people maintain a healthy weight.

Satiety: Natural fiber can make people feel fuller for longer, and they may help lower cholesterol or prevent diabetes. Rough oatmeal, whole grains, and fresh fruits and vegetables are all good sources of fiber.

Cooking methods: Opt for baked, grilled, steamed, and some raw foods rather than fried or roasted in oil. Deep-frying adds extra calories and takes away much of the nutritional content.

Exercise: This is important for overall fitness and maintaining a suitable weight. Knee pain may make some exercises more difficult, but simple stretching and other motion exercises can help strengthen the leg muscles, and this will make it easier to walk.

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Treatments For Swollen Knee

• Your treatment will depend on whats causing your swollen knee and how painful it is. Your doctor will recommend the most appropriate treatment after diagnosing the underlying cause.

  In most cases, youll be advised to take painkillers. You can also apply ice and elevate your knee to help reduce the swelling. Sometimes removing some of the fluid in your knee helps reduce the pain and stiffness.

  Other treatments include:

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Lifestyle And Home Remedies

Taking care of yourself when you have a swollen knee includes:

• Rest. Avoid weight-bearing activities as much as possible.
• Ice and elevation. To control pain and swelling, apply ice to your knee for 15 to 20 minutes every two to four hours. When you ice your knee, raise your knee higher than the level of your heart, using pillows for comfort.
• Pain relievers. Over-the-counter medicines such as acetaminophen or ibuprofen can help reduce your knee pain.

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What Else Could It Be

There are a number of other conditions that can cause pain behind the knee without typically causing much, if any, back of knee swelling visit the back of knee pain section to find out loads more.

Alternatively, it may be that there is swelling all around the knee, not just at the back, in which case, visit the swollen knee section.

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What Questions Might A Healthcare Provider Ask To Diagnose Arthritis Of The Knee

Your healthcare provider will interview you when you report your symptoms. Some questions might include:

• Does anyone in your family have arthritis of the knee?
• Does your knee swell up?
• Is your skin often red?
• Is your skin often warm?
• Do you have symptoms in one knee or both?
• How long have you had these symptoms?
• What medications do you take?
• How severe is your pain?
• Do you struggle to walk?
• Do the symptoms interfere with your daily activities?

Persistent Knee Swelling In The Adult

Welcome to this Decision Guide about persistent knee swelling. We’re sorry to hear you have this problem!

The goal of this guide is to provide information while awaiting evaluation with your doctor for persistent knee swelling or for additional information after you have seen him or her. Please keep in mind that this guide is not intended to replace a face-to-face evaluation with your doctor.

First, some background information about this guide and about knee swelling:

Knee swelling may develop for a number of reasons. If you have new, unexplained knee swelling that followed a significant injury or you have fever, this guide is not the best place to start! See your doctor first. Ligament tears, cartilage damage and fracture can follow trauma and may require urgent treatment this is particularly true if you are unable to bear weight.

This decision guide will focus on persistent knee swelling — that is, knee swelling lasting more than two or three weeks.

You’ll be asked a series of questions and depending on your answers, information will be provided and additional questions asked until the conclusion.

So, let’s get started.

Would you like to get information related to your own situation? Or would you rather start with some general information about knee swelling?

In general, one or both knees may be swollen due to

Each of these will be briefly reviewed. There are other, rarer, causes that will not be covered here.

Let’s start with Increased Joint Fluid:

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