Swollen Knee: Causes, Symptoms & Treatment Options

A swollen knee occurs when excess fluid collects in or around the knee joint due to injury, overuse, or underlying medical conditions. Treatment depends on identifying the root cause.

What Causes a Swollen Knee?

The knee is the largest and one of the most complex joints in the human body, making it susceptible to various problems that can lead to swelling. Medically known as edema, knee swelling can make everyday movements like walking and squatting difficult or even painful. Understanding the underlying causes of a swollen knee is crucial for proper treatment and management.

Swelling in the knee is typically a sign that something is wrong with the joint. As Dr. Adam Driesman, an orthopedic surgeon, explains, “Typically, knee swelling doesn’t occur without something underlying”. This swelling is often the body’s natural response to injury or inflammation, as it increases blood flow to the affected area to deliver fluids, proteins, and white blood cells needed for the healing process.

Injury-Related Causes

Injuries are among the most common reasons for knee swelling, especially in younger, healthy individuals. These injuries can occur during sports activities, accidents, or even from simple missteps in daily life.

Ligament Tears

When the ligaments in your knee are torn or stretched beyond their normal capacity, swelling often follows. The anterior cruciate ligament (ACL) is particularly vulnerable to injury during activities that involve sudden stops, changes in direction, or direct impacts. A torn ligament can cause immediate swelling as the body rushes to repair the damage.

Meniscus Tears

The meniscus is a C-shaped piece of cartilage that acts as a cushion between your femur (thighbone) and tibia (shinbone). Tears in this cartilage commonly occur during activities that involve twisting or rotating the knee while bearing weight. These tears can cause fluid buildup in the knee joint, resulting in swelling.

Dislocated Kneecap

Direct trauma to the knee can cause the patella (kneecap) to move out of its normal position, resulting in a dislocated kneecap. This injury not only causes pain and swelling but can also make the leg appear deformed or bent out of shape.

Sprains and Strains

Knee sprains occur when ligaments in the knee are torn, stretched, or damaged, while strains happen when tendons or muscles connected to the knee joint are injured. Both types of injuries typically result from twisting or overexerting the knee and can cause inflammation and swelling of varying degrees.

Fractures

The knee joint consists of four bones: the tibia, fibula, femur, and patella. A fracture in any of these bones will lead to swelling, often accompanied by bruising, sharp pain, and possible deformity of the knee. All knee fractures require medical attention and proper treatment.

Disease-Related Causes

Not all swollen knees result from traumatic injuries. Various medical conditions and diseases can also lead to knee swelling.

Arthritis

Different types of arthritis can cause knee swelling:

• Osteoarthritis: This is the most common form of arthritis, often developing with age. It occurs when the cartilage on the ends of your knee bones wears down over time, reducing the space between bones and leading to pain, stiffness, and swelling.
• Rheumatoid Arthritis: This is an autoimmune condition where the immune system attacks the joints, causing inflammation and swelling.
• Psoriatic Arthritis: Another form of inflammatory arthritis that can affect the knees and cause swelling.

Gout

Gout is a complex form of arthritis that often occurs suddenly without prior warning. It happens when uric acid crystals accumulate in the joint, causing inflammation. People with gout experience joint tenderness and redness in addition to swelling.

Bursitis

Bursae are small, jelly-like sacs that act as cushions to reduce friction between tendons and bones. When a bursa in the knee becomes irritated, often due to muscle imbalances, it can overproduce fluid, leading to knee swelling (known as knee bursitis). Overuse or direct trauma to the knee can also cause bursitis.

Infection

An infection in the knee joint can cause significant swelling, often accompanied by redness, warmth, and fever. Joint infections require immediate medical attention as they can cause serious damage if left untreated.

Overuse and Stress-Related Causes

Knee swelling can also result from overuse or putting more stress on the knee than it can handle.

Repeated Stress

This type of knee swelling develops after doing more activity than your knee can presently handle. For example, rapidly increasing your running mileage or going on a long hike after being sedentary can put extra strain on your knee joint, leading to inflammation and swelling.

Episodic Stress

Sudden, intense activities that your knee isn’t accustomed to can cause episodic stress and subsequent swelling. This might include participating in a weekend sports tournament without proper training or suddenly increasing the intensity of your workouts.

Symptoms of a Swollen Knee

Recognizing the symptoms of a swollen knee is important for seeking appropriate treatment. Here are the common signs to look out for:

Visible Swelling

The most obvious sign is visible puffiness around the kneecap, especially when compared to your other knee. The skin around your kneecap can noticeably swell due to the excess fluid in the joint.

Stiffness and Limited Range of Motion

When your knee joint contains excess fluid, you might find it difficult to bend or straighten your leg completely. This stiffness can significantly limit your range of motion and affect your ability to perform daily activities.

Pain and Discomfort

Depending on the cause of the fluid buildup, your knee might be very painful—sometimes to the point where it’s impossible to bear weight on it. The pain may be sharp, dull, or throbbing, and it can vary in intensity based on the underlying cause.

Feeling of Tightness

Many people describe a swollen knee as feeling tight, almost like having a band wrapped around the knee. This sensation is due to the pressure from the excess fluid in and around the joint.

Warmth and Redness

In some cases, particularly when the swelling is due to infection or inflammation, the knee may feel warm to the touch and appear red compared to the other knee.

When to See a Doctor

While minor knee swelling might resolve with home care, certain situations warrant medical attention.

Immediate Medical Attention

Seek immediate medical care if:

• Your knee has a change in skin color and feels warm to the touch compared with your other knee, which can indicate an infection.
• You have severe pain and cannot bear weight on the affected leg.
• Your knee appears deformed or out of place, suggesting a possible dislocation or fracture.
• You have a fever along with knee swelling, which might indicate an infection.

Non-Emergency Situations

See your doctor if:

• Self-care measures like rest, ice, compression, and elevation (RICE) don’t improve symptoms within 48 hours.
• You experience recurring episodes of knee swelling.
• The swelling persists for more than a few days.
• You have limited mobility that affects your daily activities.

Diagnosis of a Swollen Knee

To determine the cause of knee swelling, healthcare providers typically use a combination of methods.

Physical Examination

The doctor will examine your knee, checking for areas of tenderness, warmth, and visible swelling. They will also assess your range of motion and the stability of your knee joint.

Medical History

Your doctor will ask about your symptoms, when they started, any recent injuries or activities, and your medical history, including any previous knee problems or conditions like arthritis.

Fluid Analysis

In some cases, the doctor may need to extract a sample of the fluid from your knee (aspiration) to test for infection, disease, or blood from an injury. This procedure, known as arthrocentesis, can also help reduce pain and stiffness by removing excess fluid.

Imaging Tests

Various imaging tests may be ordered to get a better look at your knee:

• X-rays: These can show bone fractures, arthritis, or other bone-related issues.
• MRI (Magnetic Resonance Imaging): This provides detailed images of soft tissues like ligaments, tendons, and cartilage.
• Ultrasound: This can help visualize soft tissue structures and detect fluid buildup.

Inner Knee Pain When Driving

Treatment Options for a Swollen Knee

Treatment for a swollen knee depends on the underlying cause, but several approaches can help manage symptoms and promote healing.

Home Remedies and Self-Care

For mild to moderate knee swelling, especially from overuse or minor injuries, the RICE method is often recommended:

• Rest: Avoid activities that put stress on your knee joint.
• Ice: Apply ice to the knee for 15-20 minutes several times a day to reduce inflammation.
• Compression: Use an elastic bandage to provide support and reduce swelling.
• Elevation: Keep your knee elevated above the level of your heart when possible to help reduce swelling.

Over-the-counter pain relievers and anti-inflammatory medications like ibuprofen or naproxen can also help manage pain and reduce inflammation.

Medical Treatments

For more severe or persistent knee swelling, medical treatments may include:

• Prescription Medications: Stronger anti-inflammatory drugs or pain relievers may be prescribed.
• Joint Aspiration: Removing excess fluid from the knee can provide relief and allow for fluid analysis.
• Corticosteroid Injections: These can help reduce inflammation in the knee joint.
• Physical Therapy: A structured program of exercises can help strengthen the muscles around the knee, improve flexibility, and reduce the risk of future problems.

Surgical Interventions

In some cases, surgery may be necessary:

• Arthroscopy: A minimally invasive procedure where a small camera is inserted into the knee joint, allowing the surgeon to diagnose and treat various conditions.
• Ligament or Meniscus Repair: Surgery to repair torn ligaments or menisci.
• Joint Replacement: In severe cases of arthritis or joint damage, partial or total knee replacement may be recommended.

Prevention Strategies

While not all causes of knee swelling can be prevented, several strategies can help reduce your risk:

Maintain a Healthy Weight

Excess weight puts added stress on the knee joint, contributing to tissue and joint overload and knee degeneration that can lead to swelling. Maintaining a healthy weight can significantly reduce this stress.

Proper Exercise Techniques

Using correct form during physical activities and sports can help prevent knee injuries. This includes:

• Warming up properly before exercise
• Using appropriate equipment and footwear
• Learning and practicing proper techniques for your sport or activity
• Gradually increasing the intensity and duration of your workouts

Strengthen Supporting Muscles

Strong muscles around the knee, particularly the quadriceps and hamstrings, provide better support for the joint. Regular strength training exercises targeting these muscle groups can help prevent knee problems.

Avoid Overuse

Listen to your body and avoid pushing through pain. If you feel discomfort in your knee during an activity, take a break or modify the activity to reduce stress on the joint.

Cross-Training

Varying your activities can help prevent overuse injuries by distributing stress across different muscle groups and joints rather than repeatedly stressing the same areas.

Hip Pain Causes

Living with Chronic Knee Swelling

For those with conditions like arthritis that may cause recurring knee swelling, learning to manage the condition is essential for maintaining quality of life.

Regular Medical Care

Work closely with your healthcare provider to monitor your condition and adjust your treatment plan as needed. Regular check-ups can help catch and address problems early.

Adaptive Strategies

Modify your activities and environment to reduce stress on your knees:

• Use assistive devices like canes or knee braces when needed
• Choose low-impact activities like swimming or cycling instead of high-impact ones like running
• Make ergonomic adjustments to your home and workplace

Pain Management Techniques

Beyond medication, various techniques can help manage pain:

• Heat and cold therapy
• Massage
• Relaxation techniques
• Mind-body practices like yoga or tai chi (modified as needed)

Frequently Asked Questions

How long does it take for knee swelling to go down?

The time it takes for knee swelling to subside depends on the cause and severity. Minor swelling from overuse might resolve in a few days with proper care, while swelling from more serious injuries or conditions might take weeks or even months to fully resolve.

Can I exercise with a swollen knee?

It depends on the cause and severity of the swelling. In general, it’s best to rest until the acute swelling subsides. Then, low-impact exercises like swimming or stationary cycling might be appropriate. Always consult with a healthcare provider before resuming exercise with a swollen knee.

Is walking good for a swollen knee?

Light walking may be beneficial for some causes of knee swelling, particularly arthritis, as it helps maintain joint mobility. However, if walking causes pain or increases swelling, it’s best to rest until the symptoms improve. Again, consult with a healthcare provider for personalized advice.

What foods should I avoid with knee swelling?

If your knee swelling is related to inflammatory conditions like arthritis or gout, you might benefit from avoiding foods that can trigger inflammation, such as:

• Processed foods
• Foods high in added sugars
• Red meat and processed meats
• Foods high in purines (for gout), such as organ meats and certain seafood
• Alcohol

Can weather affect knee swelling?

Some people with arthritis or previous knee injuries report that their symptoms, including swelling, worsen with changes in weather, particularly during cold, damp conditions or before storms. While the exact mechanism isn’t fully understood, it may be related to changes in barometric pressure affecting joint tissues.