Sometimes you feel there is fluid under kneecap, and you may feel your knee is swollen. Feeling you have fluid under kneecap is an uncomfortable condition, which may have many causes, many of which may require you to visit a doctor.

Knee is one of the largest joints in our body, and holds all our weight, and allows our legs to move. Whatever bears our weight, and has a lot of functions to do, is prone to injuries, and to build-up of fluid under kneecap.

When there is build-up of fluid under kneecap, your knee will swell, which might be painful.

There is a possibility that this fluid under kneecap is not something serious, and might even get cured without any proper intervention. But it is also important for you to know what causes this build-up of fluid under kneecap, and what to do about it.

In this article we will talk about some possible causes of this condition, which are as follows:


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Knee is made up of different parts, and injury to any of the parts will cause build-up of fluid under kneecap. Your kneecap, or what is known as Patella, may itself be injured or fractured. You knee is also prone to dislocate from its own place if there is a trauma to knee, as in falling or accident. If you’re an athlete you are prone to having your knee ligaments injured. Ligaments are rope like structures that hold your knee at its proper place.

Due to sports, or any activity that involved twisting and jumping as in Dancing, may put you at a risk of meniscal tear, or tenson tear.


If your knee pain, or the swelling, is mild and manageable you can try taking rest, using ice, compressing the area, and elevating your leg. If your pain is unbearable and you can feel the build-up of fluid under kneecap increasing you will have to visit a doctor.

Based on your condition, and the severity of your injury, your doctor will recommend physical therapy, pain relievers, or in case of need- surgery.



Osteoarthritis is a condition in which the cartilage in your joints breaks down. It affects the joints of your hands, your back, knee, and hip.

As you age, you might be at an increased risk of getting Osteoarthritis. Obesity is another cause of this condition. Apart from these factors overworking and increased stress on your knees will make you prone to getting osteoarthritis.


Your doctor will prescribe medicines, and ask you to change your lifestyle. Rest, proper exercises, and controlling weight, are some of the factors that may help you get better.


Inflammatory Diseases.

Our immune system is there to help us fight against harmful things that enter our body, be it bacteria or viruses. But sometimes, for some unknown reasons, our immune system mistakenly attacks our own body. Rheumatoid Arthritis is one such condition where immune system is activated our own body. Other than Rheumatoid Arthritis many other inflammatory diseases that can affect bones are Lupus, Seronegative arthritis, Reactive and Inflammatory arthritis.

This condition involves joints, but can also involve other body parts.

When it involves joints, you may feel these symptoms:

You should always see a doctor if you feel any such symptom. Sooner it is diagnosed and treated, lesser the damage.



Bursa is a small fluid-filled sac like structure between your joints, to make the movement easier. Sometimes, overworking your knees, or some medical conditions, cause these sacs to enlarge with the fluid trapped in them. This may cause discomfort, pain, and build-up of fluid under kneecap.

Symptoms are:

The question may arise that can bursitis kill you or what are the causes and types of bursitis and how do we know we have bursitis? It is always better to see a doctor for this condition. But in case you have fever, pain that disables you, new-onset pain on moving, or increased swelling, immediately see a doctor.

Your doctor will take a sample of fluid from your knee to check for any infection. Apart from this, blood tests and imaging tests would be done for a better diagnosis.


Bone Tumors.

There are many tumors that affect the bones, some which are Osteosarcoma, Chondroma, Chondrosarcoma, Ewing Sarcoma, and Giant Cell Tumors. They usually affect you when you’re a teenager, and most affect long bones, and particularly around knee.

It is very important to focus on the symptoms, so that you don’t delay the process of diagnosing and the treatment.

Symptoms include:

Immediately see a doctor if you feel any such symptom. Your doctor will do a thorough check-up. Blood tests, imaging tests, and biopsy may be required.



Even though there are many infections that can involve your joints and make your joints swollen, but one particular infection that causes build-up of fluid under kneecap is Lyme disease.

Lyme disease is caused by bacteria, and occurs if you’re bitten by an infected tick.

Symptoms include:

If you’re bitten by a tick, it is always better to visit a doctor.



Gout is a form of arthritis, in which crystals are formed and deposited in and around the joints. This condition can cause severe pain, and swelling around the joints.

Symptoms are:


See a doctor if you have red joint, with severe pain, swelling, and a fever. It is very important to diagnose this, and to rule out other infections that may mimic these symptoms.



If you are a young adult, a female, or have high activity level, you are prone to get this condition. It is when your kneecap no longer glides smoothly over your other bones, and causes friction and pain.

This condition also causes fluid under kneecap to build-up.

Even though rest and taking over-the-counter painkillers is enough for the condition, see a doctor in case you think your pain isn’t going away.


Risk factors.


When to see a doctor?

Build-up fluid under kneecap might go away spontaneously in a few days, but it is always good to see a doctor for a definite diagnosis, and to save yourself from the complications.

See a doctor if you have:



 It is important to get the fluid under kneecap diagnosed, as it can be because of some serious causes as well. Your doctor will check your joints, ask you to move your knee.

Your doctor will order blood and imaging tests. If needed, your doctor will have to take a sample of your fluid with a needle. This is to make sure you don’t have infection or gout.



If your swelling is mild, you can take rest, use ice pack, compress the area, and elevate your legs. This method is known as RICE. Or you can take over-the-counter pain killers.

Treatment is based on the cause of the fluid under kneecap.

Sometimes pain relievers are enough for you to get better, but sometimes antibiotics, exercise, and even a knee surgery might be needed.

If the build-up of fluid under kneecap is too much, your doctor will have to drain the fluid.



If the fluid under kneecap is left untreated, the fluid might leak out around the knee and at the back of it. This may cause Baker’s cyst to form. In such case, the fluid has to be drained as this condition is very painful.

Because of fluid under kneecap the legs can’t be moved properly, this breaks down your muscles and you will lose your muscles.



You have to maintain your health to reduce the risk of having build-up of fluid under kneecap.

Some points that may help you reduce the risk are:



It is always better to get yourself checked if you feel you have fluid under kneecap. Focus on the signs like severe pain, new-onset pain, fever, severe swelling, weight loss, night sweating, and disability. These symptoms are very important to be checked.

With this being said, maintain your health, keep your weight in check, do not overwork your knees, and do healthy exercises.