This condition can be caused by trauma, overuse injuries, or an underlying disease or condition. A fluid sample from the knee may be needed for diagnosis.
A swollen knee occurs when excess fluid collects in or around your knee joint. Health care providers might refer to this condition as an effusion (uh-FU-zhun) in your knee joint.
A swollen knee may be the result of trauma, overuse injuries, or an underlying disease or condition. To find the cause of the swelling, your provider might need to test a sample of the fluid for infection, disease or blood from an injury.
Removing some of the fluid may help reduce the pain and stiffness associated with the swelling. Once the underlying cause is known, treatment can begin.
Signs and symptoms typically include:
See your health care provider if self-care measures, such as ice and rest, don't improve symptoms. Seek immediate medical attention if one knee becomes red and feels warm to the touch compared with your other knee. This can be a sign of infection within the joint.
Many types of problems, ranging from traumatic injuries to diseases and other conditions, can cause a swollen knee.
Damage to any part of your knee can cause excess joint fluid to accumulate. Injuries that can cause fluid buildup in and around the knee joint include:
Underlying diseases and conditions that can produce fluid buildup in and around the knee joint include:
The anterior cruciate ligament (ACL) is one of the key ligaments that help stabilize the knee joint. The ACL connects the thighbone (femur) to the shinbone (tibia). It's most commonly torn during sports that involve sudden stops and changes in direction — such as basketball, soccer, tennis and volleyball.
Factors that may increase your risk of a swollen knee include:
Complications of a swollen knee can include:
A swollen knee is typically the result of an injury or chronic health condition. To manage your overall health and prevent injuries:
Your health care provider is likely to start with a detailed history and physical examination. After that you likely will need tests to find out what's causing your swollen knee.
Imaging tests can help show where the problem is located. Options include:
A needle is used to remove fluid from inside your knee. This fluid is then checked for the presence of:
Treatment varies depending on the cause of the swollen knee, its severity and your medical history.
Physical therapy exercises can improve your knee's function and strength. In some situations, a knee brace may be helpful.
Treating the underlying cause of a swollen knee might require:
Taking care of yourself when you have a swollen knee includes:
You may be referred to a health care provider who specializes in musculoskeletal and joint problems.
Your health care provider is likely to ask you a number of questions. Being ready to answer them may leave time to go over points you want to discuss in depth. You may be asked: