Causes of swollen knee

Causes of swollen knee

A swollen knee is a common problem that affects one or both knees due to the accumulation of fluids inside the joint. Learn about the causes of swollen knees and how to treat them.

Swelling in your knee may occur due to various causes and diseases. Swelling may be attributed to pathological causes, such as rheumatoid arthritis or gout in the knee. It may occur when exposed to an accident or direct traumatic injury to the knee.

Treatment depends mainly on knowing the causes of a swollen knee, as determining the reason is the first step in treatment. There is no doubt that swelling will cause annoying symptoms for those who suffer from it. These symptoms are not limited to the external shape of the knee only, as this medical problem can cause severe pain and difficulty while moving, follow up with us to learn about the causes of swollen knees and the treatment methods.

What are the causes of swollen knee?

The main reason for the swelling of the knee joint is the excessive accumulation of fluids around or inside the joint; where these fluids accumulate for many reasons, including what is due to an inflammatory injury that incites an inflammatory reaction that leads to the accumulation of fluids around the injured joint, including other causes such as a rupture of the cartilage of the knee and the fluid draining out.

Swelling is a common symptom of many joint diseases. A swollen knee may be due to one of the following reasons:

Osteoarthritis of the knee joint

Osteoarthritis is one of the most common causes of the swollen knee in the elderly. This disease causes knee cartilage erosion due to the increased load on the joint, which over time, leads to damage to the joint structures and, thus, draining fluid that accumulates in the joint. This disease occurs most often in adults—those who are overweight and obese.

Swelling is usually associated with pain and stiffness in the knee; you can read more about Osteoarthritis.


Gout is one of the common causes of a swollen knee, where the patient suffers from swelling and redness in the joint with severe pain that comes in the form of attacks that intensify from time to time. Gout can affect all joints in the body, including the foot and the knee. Read more about Gout in the knee.

Meniscus tear

You often see this injury in athletes, as it is one of the most common causes of knee swelling. In the human knee, there is a cartilage called the meniscus, which is prone to injuries and ruptures when the person, especially the athlete, is exposed to a sudden sprain in the foot and leg. For more information, click on Meniscus tear.

Patellar tendinitis

The knee joint consists of a group of tendons that connect muscles with bones to ensure coordinated movement, but these tendons are at risk of inflammation when the tendon is stressed, which is one of the causes of knee swelling. You can get more details on Patellar tendinitis.

Knee fractures

Bone fracture is one of the important causes of knee swelling. When you notice sudden swelling immediately after you have been exposed to a traumatic accident, such as falling right on the knee area, then the underlying cause of the swelling may be the presence of Knee fractures.

Knee ligament rupture

The ligaments connect the bones, and the anterior cruciate ligament in the knee, the ACL, is one of the most vital ligaments in the body, which connects the femur and the shinbone (tibia). Still, it is prone to tearing and cutting during sports activities that require a quick change in the direction of movement and frequent jumping. This usually causes knee swelling among basketball players.

Rheumatoid arthritis

Rheumatoid arthritis is a common inflammatory condition in women that causes swelling in the knee joint. This disease can affect several joints of the human body and cause many symptoms. Get more information about Symptoms of arthritis in women.

Baker's cyst behind the knee

The baker's cyst is an accumulation of fluid in the back of the knee and is known as a popliteal cyst. This cyst may be associated with pain and a feeling of discomfort. It is usually formed due to joint problems and diseases such as knee arthritis or a tear in one of the meniscus cartilage.

Knee bursitis

In the normal knee, a fluid-filled sac called the cystic bursa acts as a cushion between the tendons and bones to prevent friction during movement. Still, it is at risk of inflammation, especially when overloading the joint.

Causes of knee swelling, such as arthritis, tendinitis, or ruptured ligaments, and other causes
The most important causes of knee swelling

Diagnosing the causes of swollen knee

The doctor evaluates the patient, asks about his medical history in detail, and then performs a physical examination to detect the presence of other signs and symptoms that may help reveal the cause of knee swelling.

Your doctor may use some tests to determine the causes of knee swelling, which are:


An X-ray image excludes fractures and bone abnormalities and checks for signs Arthritis Causing swelling, ultrasound imaging (echo) and magnetic resonance imaging is also helpful in denying problems with ligaments and tendons.

Joint fluid test

Using a needle, a fluid sample is withdrawn from the swelling site, and then this sample is sent to the laboratory for special tests and analyses that reveal the causes of knee swelling.

In this picture, we notice a comparison between the swelling of the knee joint and the normal knee.
Note the difference between a swollen knee and a normal knee

How to treat swollen knee

Treatment methods differ according to the causes of swelling, its severity, and the patient’s health condition. Among the most important forms of treatment are the following:

Treatment of a swollen knee at home

Resting while avoiding strenuous activities and applying ice to the swelling area helps reduce pain and swelling. In addition, raising the knee upward reduces blood flow toward the injury's site, reducing the severity of knee arthritis.

Applying pressure around the swollen joint also contributes to treating inflammation which can be done by wrapping Braces around the knee Pay attention not to wrapping tightly because it can cause side effects, such as increased swelling and pain.

Pain associated with swollen knees can be quickly relieved by taking over-the-counter anti-inflammatory medications such as ibuprofen.

Home remedies for the treatment of a swollen knee, which help treat all causes of knee swelling, such as using braces or applying ice to the site of the swelling
How to treat swollen knee at home

Exercises to treat swollen knee

Practicing Physiotherapy can improve the knee joint's function and strengthen its muscles, allowing for a better range of motion for the joint and reducing its swelling. In some cases, the physiotherapist may advise using a knee brace.

Treatment of swollen knee by using plasma injection

It is considered one of the promising methods of treating many joint diseases. Human plasma has proven effective in treating knee stiffness and relieving pain from arthritis and other conditions. Read more about Platelet-Rich Plasma for the Knee.

Treatment of Knee swelling by Arthrocentesis

Getting rid of the accumulated fluid in the knee joint by withdrawing it using a dedicated needle is one of the most effective treatments for swelling. Still, it does not address the main problem that causes swelling. Still, it is only a temporary treatment and may also be used to diagnose the causes of swelling by examining the fluid in the laboratory.

Using Knee arthroscopy is also helpful in treating swelling; a tube equipped with a lamp and a camera inserted through a small surgical incision and used to perform surgeries and repair damaged tissues in the knee joint.

In the end, the causes of the swollen knee are many and must be well known for the person to be able to treat the problem permanently. The cause of the swelling may be due to various diseases such as gout or arthritis and other diseases, and the problem may not be related to these diseases and is just an accident or injury to the knee. Therefore, it is always preferable to consult a joint specialist to diagnose the causes of swelling and treat them well.


  1. Wikipedia
  2. Medical News Today
  3. NIH

Frequently Asked Questions

When the swollen knee is accompanied by noticeable redness in addition to severe pain in the joint with a fever, then you should go to the hospital immediately, as this may be one of the signs of a bacterial infection that may spread to the rest of the body if you delay treating the joint disease.

When you notice some symptoms, such as swelling with stiffness in the joint and severe pain when touching the swelling area, you may suffer from water in the knee.

Difficulty in bending the knee, accompanied by swelling and pain when trying to turn, maybe a sign of one of the following diseases:

  • Osteoarthritis
  • Rheumatoid arthritis
  • Chronic patellofemoral pain syndrome
  • Gout
  • During the recovery phase after surgery

Knee arthritis and other diseases, such as osteoporosis and bleeding below the skin, cause swelling of the legs below the knee. Swelling may occur due to more complex conditions such as heart failure, kidney disease, and other reasons.

If you are planning for treatment in Turkey
you can talk to us here.

If you are planning for treatment in Turkey
you can talk to us here.