KNEE & HIP Replacement Center

Knee Pain and Its Causes

Arthritis is the knee's biggest enemy. Caused by injury, disease, or just the passing of time, arthritis frequently causes the pain and joint damage that can lead to knee replacement.

What is arthritis?

Arthritis is the number one cause of chronic disability in the United States. Affecting nearly 40 million Americans, it refers to more than 100 diseases that cause pain, stiffness and swelling from the inflammation of a joint or the area around joints.

Two basic types of arthritis may cause knee pain: osteoarthritis and inflammatory arthritis (most commonly rheumatoid arthritis).

	Osteoarthritis	Rheumatoid arthritis
Number affected in the U.S.	about 16 million (most common type of arthritis)	over 2 million (most common type of inflammatory arthritis)
Who is likely to get the condition	usually middle-aged and older people	75 percent are women; most often begins between 30 and 60, but can develop at any age
Definition	joint disease that gets worse over time; does not cause swelling in the joints (not inflammatory)	inflammatory condition (causes joint swelling) in which the immune system mistakenly attacks the tissue that lines and cushions the joints
Why it causes pain	cartilage that cushions the bones of the hip starts to erode, eventually allows the bones of the joint to grind or rub together	cartilage wears away and the cushioning fluid in the joint (the synovium) becomes inflamed (swollen) - inflammation causes chemicals to be released that damage the cartilage and bone of the affected joint
Symptoms	pain and stiffness	pain and swelling