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Arthritis and Your Knee

An estimated 50 million adults in the U.S. have been diagnosed with some form of arthritis, or other disease of the musculoskeletal system.  This includes (based on 2005-2007 estimates) 27 million people with OA and 1.5 million people with RA.

Any form of arthritis may cause the knee joint to become stiff, making it difficult to bend or extend the knee, and may cause pain. The two most common forms of Arthritis are Osteoarthritis and Rheumatoid Arthritis. 

  • Osteoarthritis is a slowly progressive degenerative disease in which the joint cartilage gradually wears away or loses flexibility. Without cartilage, the bones have no cushioning to protect them from grinding against each other. With OA, the knee joint may ache, be painful or be stiff first thing in the morning, during and after physical activity, and even after periods of inactivity.[1]

  • Rheumatoid Arthritis is an inflammatory disease in which the immune system can destroy the joint cartilage.  It can cause the soft tissue lining the inside of joints (also called the synovial membrane) to produce too much fluid, causing swelling known as “water on the knee.”[2] RA can occur at any age. With RA, the knee can become swollen, red, and hot to the touch.[3]
  • Post-traumatic arthritis – another cause of knee problems that is similar to osteoarthritis – can develop after an injury to the knee. This type of arthritis may develop years after a bone fracture, a tear to cartilage called the meniscus, or injury to the two major ligaments that stabilize the knee – the anterior or posterior cruciate ligaments (ACL/PCL).[4]


[1] Arthritis Foundation. What is Osteoarthritis? Available at Accessed on March 27, 2011.

[2] American Academy of Orthopaedic Surgeons. Total Knee Replacement. Available at Accessed on April 1, 2011.

[3] National Institute of Arthritis, Muskuloskeletal and Skin Diseases. Knee Problems. Available at Accessed on March 27, 2011.

[4] American Academy of Orthopaedic Surgeons. Arthritis of the Knee. Available at Accessed on April 1, 2011.

The information listed on this site is for informational and educational purposes and is not meant as medical advice. Every patient's case is unique and each patient should follow his or her doctor's specific instructions. Please discuss nutrition, medication and treatment options with your doctor to make sure you are getting the proper care for your particular situation. The information on this site does not replace your doctor's specific instructions.