10 Frequent Causes Of Knee Swelling

By Tiffany Tseng. May 7th 2016

For an active person, a swollen, painful knee can be debilitating. Not only can knee swelling be extremely painful and inflamed, it can also reduce or completely limit a person’s range of motion in the legs. If the swelling is ignored or left untreated, it can worsen to the point that the knee can become unusable. Some of the injuries that cause knee swelling can range from mild to serious, and treatments can also vary. However, before self-diagnosing any conditions, be sure to first seek a licensed doctor’s opinion to avoid any misdiagnoses that can make the condition worse. Read on to learn 10 common causes of knee swelling.

Knee Sprain

One of the most common causes of knee swelling is a ligament sprain, or excessive straining of the knee. During this time, the knee ligament could be torn or stretched, resulting in pain, swelling, bruising, and limited ability to move the knee. Since the knee is one of the most commonly used joints on the body, a sprung knee is usually the first cause to be questioned.

[For more information, check out A Quick Guide To Knee Sprains]

Knee Bursitis

Knee bursitis is characterized by the inflammation of one of the 11 bursas located around and on the knee joint. Bursas are meant to cushion the knee joint and reduce joint friction, but repeated trauma to the bursa can cause it to be inflamed, swollen, and painful. Bursitis in the knee can be treated by a combination of rest and therapy. In serious cases, it may require surgery.

Baker’s Cyst

Also known as a popliteal cyst, a Baker’s cyst is a fluid filled bulge behind the knee that can cause tightness, limit range of knee movement, and possibly pain, along with swelling. This cyst forms when inflammation is present in the knee joint, and the knee produces excessive synovial fluids that the body cannot reabsorb. Usually, fluid drainage, medication, or physical therapy can help alleviate knee swelling associated with Baker’s cyst.


A type of arthritis, gout is characterized by sudden attacks of pain, accompanied by extreme tenderness and swelling of the joints. It can easily happen to the knees, and can be debilitating. Gout happens when crystals are formed in the knee joint due to the accumulation of urea. The crystals can irritate and inflame the surrounding joint and tissues. Fortunately, it is treatable, so be sure to see your doctor for gout pain alleviation and treatment.

[For quick, temporary relief, read up on gout pain management in How To Relieve Gout Pain At Home]

Blood In The Joint

When significant damage happens to the knees, massive bleeding can occur into the joint spaces. This condition is known as haemarthrosis, and can cause excessive knee swelling, warmth, stiffness, and bruising. Be sure to go to the hospital immediately to have it treated if you suspect you are bleeding into the knee joint space.

Damage To The Menisci

The menisci are rubbery pads between the two upper and lower knee bones, and they act as cushions and shock absorbers as a person moves and uses the knee. If the menisci are damaged via tearing, wearing, or twisting, the knee will become swollen and hard to move. Treatment can vary, and surgery may be needed in more serious cases.

[Related – 10 Common Causes Of Knee Pain]

Knee Tumors

Tumors in the knee will cause excessive knee swelling. One of the more common benign tumors, lipoma arborescens, is characterized by abnormal deposits of fatty tissue within the knee joint space. Typically, tumors can be safely removed via surgery.

[Related – 10 Common Types Of Knee Surgery]


If harmful bacteria or organisms get into the joint fluid of the knees, an infection may occur and cause pain, warmth, and excessive swelling of the joint. Bacteria and organisms can be introduced via post-knee-surgery recovery complications, a deep knee puncture, or knee trauma. Treatments may vary depending on the type and cause of infection, so be sure to see a doctor regarding the methods of recovery.


Perhaps the most common form of arthritis that causes pain and swelling of the knee is osteoarthritis. This condition is caused by aging, normal wear and tear, but individuals who had prior knee infections, trauma, or injury are even more susceptible to the condition. Osteoarthritis is characterized by the wearing down of knee cartilage and fluid accumulation in the joint space. Obesity can also be a contributing factor.

Osgood-Schlatter Disease

This condition is more prominent and common in teenagers who are active in sports. This condition is caused by a sprain or overuse of the thigh muscles, rather than on the knee joint itself, and is characterized by knee pain, swelling, and painful lumps around the joint.

For any instance of knee swelling, be sure to elevate the legs and use an ice pack to try and reduce the swelling. If the pain or swelling exceeds more than 3 days, or becomes worse, be sure to see a healthcare professional. Do not wait too long, because certain conditions can cause irreversible damage if left untended for too long. To be safe, remember to always see a healthcare professional before implementing any self-remedies!


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