Swollen Knee: Causes, Treatments & Prevention

A swollen knee happens when there’s too much fluid in or around the knee joint. People may call it “water on the knee” or “knee joint effusion.” This swelling can come on suddenly or slowly, ranging from mild to severe, and can make it hard to move your leg comfortably. It could also be a sign of a more serious medical problem.

Knee swelling usually occurs after a knee injury, but it can also show up without an obvious reason, often due to an underlying knee issue like gout. Even if you can’t see it, sometimes small amounts of knee swelling can still be painful. In other cases, the swelling is more visible and widespread.

In this article, we’ll look at common causes of knee swelling, the different types of swelling, how to tell if it’s a serious problem, and the best ways to treat swollen knees.

What is Knee Swelling?

Knee swelling means there’s extra fluid in or around your knee joint. The knee joint is the big connection between your thigh bone and shin bone, including the kneecap. It’s the body’s largest joint with cartilage, muscles, ligaments, and nerves.

Many things, like injuries or health issues, can make your knee swell. When your knee swells, you might also have:

  1. Pain in the knee.
  2. Feeling like your knee is stiff or tight.
  3. Redness or a change in color.
  4. Warmth or heat in the area.

For most cases, you can treat knee swelling at home with rest and over-the-counter meds. But if you have a big injury or sports accident, see a doctor. Also, talk to a healthcare pro if the swelling doesn’t go away after a few days, if it hurts a lot, or if you can’t move your knee well.

Types of Knee Swelling

There are different types of knee swelling:

  1. Rapid Swelling After an Injury: This happens right after an injury, usually due to bleeding into the joint (haemarthrosis). It causes intense pain and a quickly ballooning knee, often with bruising. Seek urgent medical help if you experience this.

  2. Delayed Swelling After an Injury: Knee swelling can appear a few hours to days after an injury due to increased synovial fluid (knee effusion). It’s usually less severe and doesn’t feel as tense.

  3. Gradual Swelling Without an Injury: When knee swelling develops slowly without a specific injury, it’s a sign of an underlying knee condition. It may come and go, and its severity is usually mild to moderate.

  4. Rapid Swelling Without an Injury: Occasionally, a swollen knee can suddenly appear without prior injury, often linked to joint infections. Immediate medical attention is necessary in such cases.

Swollen Knee Symptoms

If you think your knee is swollen, look for these usual signs:

  1. Swelling: You’ll see puffiness around your kneecap, more than your other knee.

  2. Stiffness: Extra fluid in the knee can make it tough to fully bend or straighten your leg.

  3. Pain: Depending on why the swelling happened, your knee might hurt, making it hard to bear weight on it.

Causes of Swollen Knee

Your knee can swell suddenly for various reasons. Here are some common causes:

  1. Bursitis: This happens when the small sacs of fluid in your knee (bursae) get irritated, causing inflammation and swelling. It often occurs from kneeling a lot or getting a blow to the knee. To diagnose it, your doctor may check you and do X-rays or MRIs. Treatment can include compression, ice, elevating your leg, resting, and taking anti-inflammatory drugs for pain relief.

  2. Arthritis: Arthritis is a common reason for knee swelling. Different types of arthritis can lead to this symptom, like osteoarthritis (from cartilage damage), rheumatoid arthritis (an immune system issue), juvenile arthritis (in kids under 16), reactive arthritis (often after a genital or urinary tract infection), infectious arthritis (caused by infections), and gout (from too much uric acid). Diagnosis involves looking at your symptoms, medical history, blood tests, and imaging. Treatment depends on the type and may include pain meds, lifestyle changes, physical therapy, corticosteroids, disease-modifying drugs, assistive devices, or surgery.

  3. Acute Injuries: Sports, exercise, or accidents can lead to sudden knee swelling. Common injuries include sprained ligaments or muscles, tendonitis from overuse, and cartilage tears from trauma. Diagnosis often needs imaging like X-rays, CT scans, or MRIs. Treatment may involve rest, using braces or devices, anti-inflammatory meds, physical therapy, or surgery.

  4. Infections: Some infections can cause knee swelling. Conditions like lupus, an autoimmune disease that attacks joint tissues, and Lyme disease, transmitted by ticks and causing flu-like symptoms, rashes, and joint swelling, are examples. Diagnosis involves medical tests, and bacterial infections like Lyme disease can be treated with antibiotics.

Diagnosis of a Swollen Knee

To figure out why your knee is swollen, your doctor will start by asking about your medical history, any recent accidents, or past injuries. They will also give your knee a close look.

During the examination, your doctor will notice different things based on the cause of the swelling. If the swelling is inside the knee joint, your kneecap will still be easy to feel under the skin, even though it might seem a bit pushed out. But if the swelling is in the soft tissues around the knee, it can make the kneecap harder to find.

Your doctor might also ask you to do a “straight leg raise” test, where you sit on a table and stretch your leg out. How well your knee moves during this test can give clues about what’s causing the problem.

Based on what they find, your doctor might recommend some tests:

  1. Joint Aspiration (Arthrocentesis): They’ll use a needle to take out some fluid from your joint. By analyzing this fluid, they can see if there’s an infection, inflammation, blood, or uric acid crystals.

  2. Imaging Studies: This usually means getting an X-ray or a CT scan of your knee. X-rays give a clear picture of the bones, while CT scans create a 3D view inside your knee.

Risk Factors for Swollen Knees

There are some things that can make you more likely to have swollen knees:

  1. Age: When you get older, your chances of getting swollen knees from arthritis go up.

  2. Sports: If you play sports where you twist your knee a lot, like basketball, you might hurt your knee and make it swell.

  3. Obesity: Being overweight puts more pressure on your knee joint, which can make your knee wear out and swell up.

How Do You Treat a Swollen Knee?

Dealing with a swollen knee depends on why it’s swollen. If you hurt it or had an accident, see a doctor right away. If it’s swollen for other reasons, you can start treating it at home. Here’s a simple guide:

  1. Rest: Avoid activities that strain your knee. Let it heal without extra stress.

  2. Ice: Put a cold pack on your knee for 15 minutes a few times a day. This reduces pain and swelling. Make sure to wrap the ice pack in a thin towel.

  3. Compression: Use an elastic bandage to gently wrap your knee. This can help reduce swelling.

  4. Elevation: Whenever you can, raise your knee above your heart level. This helps reduce swelling.

  5. Over-the-Counter Medications: You can try over-the-counter pain relievers like NSAIDs or acetaminophen to ease pain and swelling. But don’t use them for more than ten days without talking to a doctor.

If your knee problem is due to an injury or a health issue, your doctor may suggest more treatments like:

  • Crutches: These can help you move around without hurting your knee more.

  • Knee Brace: It stabilizes and protects your knee.

  • Physical Therapy: Special exercises and therapy to help you recover.

  • Corticosteroids: Medications to reduce swelling in some cases.

  • Surgery: This is for severe cases like torn ligaments or meniscus. Knee arthroscopy may be needed to fix the problem. For arthritis-related swelling and pain that won’t go away, your doctor might recommend knee replacement surgery as a last option.

Remember, surgery is usually the last choice, and your doctor will talk to you about it if it’s necessary.

How to Prevent Knee Swelling

To keep your knees healthy and prevent swelling, follow these easy steps:

  1. Wear the Right Gear: Use the proper protective equipment for your sport or activity.

  2. Listen to Your Body: Don’t ignore knee pain; take a break if you feel discomfort during or after physical activities.

  3. Rest and Recover: Give your body time to heal after intense workouts or sports.

  4. Warm-Up and Stretch: Before exercising or playing sports, do warm-up exercises and stretches to prepare your muscles and joints.

  5. Cool Down and Stretch: After physical activity, cool down and stretch to prevent stiffness and swelling.

Here are some extra safety tips:

  • Keep Your Space Clear: Make sure your home and workspace are free from clutter to avoid accidents.

  • Use the Right Tools: Use appropriate tools for reaching high places; avoid standing on unstable surfaces like chairs or tables.

  • Mobility Aids: If you have difficulty walking or are at risk of falling, use a cane or walker for support and stability.

When to Seek Medical Help for a Swollen Knee

If you’re wondering when to see a doctor for a swollen knee, follow this simple guide:

  1. Seek medical attention if you hurt your knee in an accident, fall, or any traumatic event that caused swelling.

  2. If your knee is swollen without a traumatic cause and home remedies don’t help after a few days, consult a healthcare provider.

  3. Go to the emergency room if:

  • You’re in severe pain because of your swollen knee.
  • You can’t move or use your knee due to the swelling.
  • You experienced a major trauma, like falling from a height or being in a car accident.

If you need more guidance, you may make an appointment with our online pain management consultation

Need professional help to relieve chronic pain? Book an online consultation with physical therapist Dr. Olivia Patel.

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I'm Dr. Olivia Patel, a physical therapist specializing in helping people with neck, back, and knee pain. Instead of resorting to invasive treatments or surgeries, I use natural and non-invasive remedies to help my clients alleviate their agonizing pain and regain the joy of living a pain-free life. If you're interested in learning about my approach, click the button below to schedule a call with me.