Arthritis and Diseases that Affect the Knee
From cartilage breakdown to infections in the joint, problems that may be to blame for painful knees.
Virtually any form of arthritis can affect the knee, and cause pain and swelling. These include:
Osteoarthritis. The most common form of arthritis, osteoarthritis is a chronic condition characterized by the breakdown of the cartilage that cushions the ends of the bones where they meet to form joints. The breakdown of cartilage causes the bones to rub against each other, causing stiffness, pain and loss of movement in the joint. The knee is one of the joints most commonly affected by osteoarthritis.
Rheumatoid arthritis. Rheumatoid arthritis is a chronic inflammatory disease of the joints which occurs when body’s immune system – which normally protects us from infection – mistakenly attacks the synovium, the thin membrane that lines the joints. The result can be joint damage, pain, swelling, inflammation, loss of function and disability. In addition to the knees, rheumatoid arthritis, commonly affects the hands, wrists, feet, elbows and ankles.
Juvenile arthritis. Juvenile arthritis is the term used to describe arthritis when it begins at age 16 or before. There are several different types of juvenile arthritis, including juvenile rheumatoid arthritis (JRA) and juvenile idiopathic arthritis (JIA). Many can cause pain and swelling of the knee.
Gout. Gout is a form of arthritis that occurs when excess uric acid, a bodily waste product circulating in the bloodstream, is deposited as needle-shaped monosodium urate crystals in tissues of the body, including the joints. For many people, the first symptom of gout is excruciating pain and swelling in the big toe – often following a trauma, such as an illness or injury. Subsequent attacks may occur off and on in other joints, primarily those of the foot and knee, before becoming chronic.
Reactive arthritis. Reactive arthritis is a chronic form of arthritis that often occurs following an infection of the genital, urinary or gastrointestinal system. Features of reactive arthritis include inflammation and swelling of the joints (primarily the knee, sacroiliac joints and joints of the feet), eyes and structures within the gastrointestinal or genitourinary tracts, such as intestines, kidneys or bladder.
Lyme disease. Lyme disease is an infectious disease characterized by a skin, rash, joint swelling and flu-like symptoms. The disease is caused by the bite of a tick infected with a bacterium called B. burgdorferi. The knee is often the first joint affected by Lyme disease.
Lupus. Lupus, or systemic lupus erythematosus, is a chronic autoimmune disease, meaning the body's immune system creates antibodies that attack healthy tissues. In addition to causing inflammation in the knee and other joints, lupus can affect many organs, including the skin, heart, lungs, and kidney.
Ankylosing spondylitis. Ankylosing spondylitis is a form of arthritis that primarily affects the spine, causing inflammation in the spine that can lead to chronic pain and stiffening of the spine. In some people, particularly younger people, it begins with pain and swelling in the knee rather than the spine.
Psoriatic arthritis. Psoriatic arthritis is a form of arthritis accompanied by the skin disease psoriasis. The skin disease often precedes the arthritis; in a small percentage the joint disease develops before the skin disease.
Infectious arthritis. Also called septic arthritis, infectious arthritis refers to arthritis that is caused by an infection within the joint. Infectious arthritis is often cause by bacteria that spread through the bloodstream to the joint. Sometimes it is caused by viruses or fungi.