Swelling in the knee can reduce mobility and cause pain. To quickly ease the swelling, a person can try resting, applying ice, elevating the knee, anti-inflammatory medications, massages, and gentle exercises.
Swelling of the knee may result from overuse, injury, or arthritis. A person may be able to ease the swelling at home, but in some cases, professional treatment is necessary.
This article describes some of the more common causes of swelling in the knee and various ways to reduce it quickly.
A range of issues can cause swelling in the knee, including:
Any of the following might result in a swollen knee:
- A sprain: This is a stretched or torn ligament. Ligaments are bands of fibrous tissue that connect bones to other bones. Knee sprains might result from a forceful impact or twisting of the knee.
- A strain: This is a stretched or torn muscle or tendon. Tendons are bands of fibrous tissue that connect muscles to bones. Knee strains can occur following sudden movement or twisting of the knee.
- Torn cartilage: The menisci are a pair of crescent-shaped pads of cartilage that sit inside each knee joint. They help prevent friction between the bones that make up the knee. Sudden twisting of the knee can result in a torn meniscus.
- Tendinitis: This is inflammation of a tendon. Tendinitis of the knee can be due to overuse of the knee joint, typically from activities such as running, jumping, and cycling.
The bursae are fluid-filled sacs that help reduce friction within a joint. They can become inflamed and produce excess fluid, leading to swelling of the joint.
Prepatellar bursitis is the medical term for swelling of the kneecap’s bursae. This can result from:
- continual pressure on the front of the knee, possibly caused by frequent kneeling
- injury to the front of the knee
- infection of the bursae
Some symptoms include:
- rapid swelling of the front of the knee
- redness or warmth around the knee
- pain that typically occurs during or following activity
Arthritis causes inflammation of one or more joints.
There are more than 100 types of arthritis. Two that commonly affect the knees are osteoarthritis and rheumatoid arthritis.
Osteoarthritis is degenerative, it causes the cartilage of a joint to gradually wear away.
In the knee, it can cause the cartilage that cushions the ends of the bones that make up the knee joint to degenerate. Over time, this causes the bones to rub together.
A person might experience:
- joint pain and stiffness
- a limited range of motion in the joint
- clicking or cracking when bending or extending the joint
- swelling around the joint
- weakness of the muscles around the joint
- instability or buckling of the knee joint
- the development of growths called bone spurs
Rheumatoid arthritis is a chronic autoimmune disease in which the immune system attacks healthy tissues, including cartilage and bone.
In the knee, this can cause the synovial membrane lining the joint to swell. It can lead to pain, visible swelling, and a reduced range of motion in the knee.
Arthritis from an infection
An infection can occur in the fluid or tissues of the joints. A doctor might refer to it as septic arthritis. This is an emergency, and it requires urgent surgery.
The infection may be viral, fungal, or bacterial, but the most common culprit is Staphylococcus aureus, a type of bacteria.
The infecting pathogen may enter the knee joint through a wound, or the infection may spread from another part of the body.
The following factors can increase the risk of septic arthritis:
- older age
- rheumatoid arthritis
- disorders of the lung or liver
- alcohol use disorder
- intravenous drug use
- a suppressed immune system
- a systemic blood-borne infection
Also, a person who has had septic arthritis in the past has an increased risk of the issue returning.
Below are some techniques for reducing the swelling at home:
Avoid any activity that may have caused the knee to swell. This gives the joint a chance to heal. It is particularly important to avoid any weight-bearing exercises, which may worsen a knee injury.
However, gently stretching and straightening the knee from time to time will keep it flexible as it heals.
Applying ice to the knee, for 15–20 minutes at a time, can reduce swelling. It causes the blood vessels near the joint to constrict, decreasing blood flow and inflammation.
Do not apply ice directly to the skin, as this can cause burns. Instead, place it in a sealable plastic bag, then wrap the sealed bag in a clean towel or cloth before applying it to the skin.
Using a compression bandage or sleeve keeps fluid from collecting in and around the joint. This can help prevent or reduce swelling.
Opt for a wider bandage, which provides more pressure without cutting off circulation. The wrapped bandage should be firm but not tight.
Elevating the knee
When the person is resting, their swollen knee should lie above the level of their heart. This helps drain excess fluid from the joint and reduces blood flow to it. Both help ease swelling.
Regular cushions or pillows often do the trick, but special leg elevation pillows are also available.
Taking anti-inflammatory medication
Taking nonsteroidal anti-inflammatory drugs (NSAIDs) should help reduce swelling and inflammation of the knee joint and relieve pain.
Doing gentle exercises
Isometric exercises contract a particular muscle or group of muscles without causing the joint to move.
A physiotherapist may develop a plan of these exercises to help strengthen and support the muscles around the knee while reducing fluid buildup in the joint.
Massaging the knee
Massage can help drain excess fluid away from the knee. A person might perform the massage themselves or visit a qualified massage therapist.
Consult a doctor if swelling of the knee joint does not improve with several days of rest and home care.
Other symptoms that indicate a need for medical attention include:
- redness or warmth around the knee
- discoloration of the skin below the knee
- any other unusual appearance of the knee
- clicking or locking of the knee
- pain, numbness, or tingling of the skin below the knee
- severe or persistent knee pain
- an inability to put weight on the knee
- pain that persists when there is no weight on the knee
- an inability to straighten the knee joint
- a fever
Swelling of the knee may result from overuse, injury, or a type of arthritis.
Home care, such as using ice and elevating the area, may reduce the swelling and support healing, but professional treatment may be necessary.
See a doctor for severe or persistent swelling of the knee or if the swelling is accompanied by any other concerning symptom.