Everything You Need To Know About Knee Bursitis

What Is Knee Bursitis?

Your knee is a complex joint made up of bones, muscles, tendons, and ligaments that work together to support movement. This joint connects the thigh bone and shinbone (femur and tibia). At the front of your knee, there’s a small bone, the kneecap (patella), that helps protect the joint.

Knee bursitis condition with fluid filled bursa in leg joint outline diagram. Labeled educational medical liquid growth anatomy scheme with chronic leg inflammation pathology vector illustration.

These structures are kept in place by strong bands of tissue:

• Ligaments connect the bones and provide stability
• Tendons attach muscles to bones, helping control movement

Surrounding these structures are small, fluid-filled sacs called bursae (singular: bursa). Each knee contains several bursae, which act as cushions between your bones, tendons, and muscles. Their main job is to reduce friction and pressure during movement, keeping knee movements smooth and fluid.

Knee bursitis occurs when one of these bursae becomes swollen and irritated, leading to pain and swelling in a specific area of the knee. This inflammation can limit your ability to walk, bend, or kneel.

Types Of Knee Bursitis

There are 12 bursae in the knee, and 5 of them play a primary role in cushioning and protecting the joint during movement. Different bursae can become inflamed, each leading to symptoms in different areas.

The most common types of knee bursitis include:

• Anserine Bursitis. Swelling and pain on the inner side of your knee, just below the joint. This often affects people who run or have arthritis.
• Infrapatellar Bursitis. Also called “clergyman’s knee,” this involves the bursa just beneath the kneecap. Often caused by frequent kneeling or pressure.
• Prepatellar Bursitis. Sometimes called “housemaid’s knee,” this affects the bursa at the front of the kneecap. It results from frequent kneeling and can make the front of the knee appear puffy and sore. The prepatellar bursa is the most commonly affected one in the knee.^[1]
• Suprapatellar Bursitis. Swelling occurs above the kneecap, between the thigh muscle and the bone, usually from overuse or injury.

Typically, bursitis causes pain, swelling, and difficulty moving your knee. However, the location and intensity of the symptoms depend on which bursa is affected.

Common Causes Of Bursitis In The Knee

Knee bursitis can have several underlying causes. Understanding what triggered your symptoms is the first step toward finding adequate care. The main causes include repetitive pressure, trauma, infection, poor movement patterns, and certain health or lifestyle factors.

Repetitive Pressure Or Overuse

Kneeling, squatting, or leaning on your knees for long periods places repeated pressure and stress on the bursae. Over time, this constant friction may cause the bursa to become irritated and swollen. In these cases, the irritation builds up gradually as the tissue becomes inflamed from continued stress.

People whose jobs or activities involve frequent kneeling, like gardening, cleaning, or certain sports, are at higher risk. Pes anserine tendo-bursitis, which involves inflammation of both the tendons and the bursa on the inner side of the knee, makes up about 2.5% of knee pain cases in athletes.^[2]

Trauma Or Injury

A sudden blow or fall onto the knee can directly damage the bursa, causing it to fill with extra fluid. Shortly after the injury, the affected area typically becomes swollen and tender. Even minor trauma, such as bumping your knee against a hard surface, can sometimes be enough to trigger bursitis, especially if the area is repeatedly stressed.

Infection

About 30% of bursitis cases are caused by infection, a condition known as septic bursitis.^[3] This usually happens when bacteria, most often Staphylococcus aureus, enter the bursa through a scrape, cut, or puncture wound near the knee.

The bacteria cause inflammation and can fill the bursa with pus, making the area red, warm, and extremely painful. Prompt medical attention is necessary, as untreated infections can spread to other parts of the joint or body.

Poor Biomechanics Or Muscle Imbalance

Problems with posture or conditions like scoliosis can change the way you walk. This leads to uneven pressure, which can irritate bursae in specific locations and increase the risk of bursitis. For example, weakness in the hip or thigh muscles may force your knee to work harder, straining the bursae on one side of the joint.

Similarly, pes anserine bursitis tends to occur more often in people with flat feet.^[4] This is because flat feet can lead to abnormal alignment of the leg, creating more pressure on the inner side of the knee, where the pes anserine bursa is located.

Obesity

Carrying extra body weight increases the load on your knees. The additional pressure requires the bursae to work harder to cushion the joint, which may increase the risk of irritation and swelling.

Additionally, research from 2021 shows that people with obesity face a greater risk of developing inflammatory conditions like synovial inflammation, which is the inflammation of the joint’s lining.^[5] Being overweight is also linked to conditions such as osteoarthritis, diabetes, and gout, which may contribute to a greater likelihood of developing bursitis.

Underlying Health Conditions

Some medical conditions can increase your risk of developing knee bursitis. These health issues can either lead to persistent inflammation, cause crystals to build up in the joints, or change how your immune system responds. When these conditions are present, your bursae may become irritated more easily. They include:

• Rheumatoid Arthritis. This is an autoimmune disease in which your immune system attacks healthy joint tissues, causing swelling and pain. The chronic inflammation from rheumatoid arthritis can spread to the bursae around your knee, making them more likely to become irritated and swollen.
• Gout. Gout is a type of arthritis caused by a buildup of uric acid crystals in the joints. Sometimes, these sharp crystals collect in the bursae, triggering intense pain and inflammation.
• Pseudogout. Similar to gout, pseudogout develops when a different type of crystal (calcium pyrophosphate) builds up in the joints and bursae, leading to swelling and pain.
• Diabetes. Diabetes impacts blood flow, nerve function, and immune response, affecting the body’s ability to fight off inflammation and infection. This increases your risk of both non-infectious and infectious bursitis. Research suggests that pes anserine bursitis may impact as many as one in four people with diabetes, with women being affected more often than men.^[6]
• Lupus. Lupus is another autoimmune disease that can cause inflammation throughout your body, including the joints and surrounding tissues, such as the bursae.

Signs And Symptoms To Look Out For

Symptoms can vary in location and intensity depending on the cause and type of bursitis. Some may develop over time, while others appear shortly after an injury. Common ones include:

• Bump On Knee Cap: A bump on the kneecap is a raised area, often from injury, bursitis, or bone overgrowth.
• Knee Pain: Knee pain is discomfort in or around the joint, often caused by injury or arthritis. Read more about Knee Pain.
• Lump On Knee Cap That Moves: A lump on the kneecap that moves is a soft or firm bump, often caused by a cyst or swollen bursa.
• Swelling Above Kneecap: Swelling above the kneecap refers to fluid buildup, often caused by bursitis or soft tissue injury.
• Swelling Below Kneecap: Swelling below the kneecap refers to inflammation, often caused by tendonitis or strain of the patellar tendon.
• Tenderness: Tenderness is pain when touching an area, often due to injury or inflammation. Read more about Tenderness.

Diagnosing Knee Bursitis Accurately

Getting the correct diagnosis is key to treating knee bursitis and ruling out other problems. Your healthcare provider may use a combination of methods to pinpoint the cause of your symptoms:

• Physical Examination: Your provider will check your knee for swelling, warmth, and tenderness. They may gently press on different areas or ask you to move your leg to see how movement is affected.
• Blood Tests: Blood tests are used to check for signs of infection, inflammation, or health conditions like gout or rheumatoid arthritis that could trigger bursitis.
• Knee X-rays: While bursae are not visible on X-rays, this imaging test can help rule out bone problems, such as fractures or arthritis.
• MRI Imaging or Ultrasound: These imaging tools create detailed pictures of soft tissues in your knee. They can help identify inflammation, fluid buildup, or other joint conditions that may not be seen on X-rays.
• Joint Aspiration: In this procedure, a physician uses a thin needle to remove fluid from the swollen bursa. This sample can be tested for infection or crystals (such as those seen in gout or pseudogout) to better understand the cause of your bursitis.

When To Seek Support for Your Knee Condition

Not all knee pain means you need urgent care, but certain symptoms may indicate a more serious problem. It’s important to watch for these warning signs and seek medical attention if they appear:

• Severe Or Persistent Knee Pain: Intense pain, or pain that doesn’t improve with rest, may be a sign of a more serious injury or infection.
• Rapid Or Sudden Swelling: Quick onset can indicate bleeding, infection, or acute injury inside the knee.
• Redness And Warmth Over The Knee: These are signs of active inflammation or possible infection that should not be ignored.
• Fever Or Chills: Systemic symptoms like fever or chills, along with knee swelling, may mean the bursa is infected. This can develop into a serious condition quickly and needs urgent care.
• Limited Range Of Motion: If you cannot fully bend or straighten your knee, it could mean there is severe swelling or injury to other joint structures.
• Recurrent Bursitis: Bursitis that keeps coming back may be due to an ongoing underlying condition, ongoing joint stress, or chronic diseases such as diabetes.
• A Growing Or Persistent Lump Near The Knee: While most are benign, some lumps that don’t go away or get bigger may indicate other conditions that need attention.

Treatment Options That May Help Address Knee Bursitis

Treatment options for bursitis depend on the underlying cause, making getting an accurate diagnosis an essential step. In some cases, bursitis caused by minor injuries may improve with at-home care. However, if other structures are involved or joint problems are due to conditions like diabetes or rheumatoid arthritis, treatment should aim to address the contributing factors behind the condition.

• Bursectomy: Bursectomy is a surgical procedure that involves removing a bursa, a fluid-filled sac that helps reduce friction between tissues.
• Kinesio Tape Treatment: Kinesio tape is a flexible adhesive tape applied to muscles or joints. It is used to support movement and may help reduce discomfort. Read more about Kinesio Tape Treatment.
• NSAIDs Treatment: NSAIDs (nonsteroidal anti-inflammatory drugs) are medications commonly used to manage inflammation and discomfort in muscles and joints. Read more about NSAIDs Treatment.
• PRP Injections for Knee: PRP injections use a patient’s own platelet-rich plasma and may help support tissue function in joints, tendons, or ligaments. Read more about PRP Injections for Knee.
• Tendon Repair: Tendon repair is a surgical procedure to reconnect torn or damaged tendons and may help support joint function.