How does the knee normally work?

Normal knees follow a circular motion, the bones of the upper and lower leg moving in harmony separated by shock-absorbing cartilage and synovial fluid, which acts as a lubricant.

Anatomy of a Normal Knee

How does arthritis affect the knee?

When the cartilage lining in the knee wears away, the bones start to rub against each other, causing significant pain and swelling. The most common cause of this is a condition known as osteoarthritis.

Anatomy of a Arthritic Knee

Osteoarthritis is the most common form of arthritis in the United States

Osteoarthritis (OA) is sometimes called degenerative arthritis because it is a "wearing out" condition involving the breakdown of cartilage in the joints. Joint cartilage is a gel-like protective tissue found at joint surfaces, which provides support and lubrication during movement. When cartilage wears away, the bones rub against each other, causing pain and stiffness.

What is OA?

Osteoarthritis is the most common form of arthritis in the United States.2 You may have heard OA referred to as "wear and tear" arthritis. When OA begins to affect one of your joints, a series of reactions take place that actually begin to degrade your once-healthy bone and the soft tissue around the joint—tendons and cartilage. Once the cartilage that normally cushions and protects the bones of the joint breaks down, the bones of your joint eventually rub directly against each other. Your body reacts to this by creating bone spurs and the joint capsule itself may thicken and weaken. Inflammation eventually sets in.

Doctors talk about 2 kinds of OA. Primary OA often refers to "everyday wear." Secondary OA is considered the result of a malaligned joint, being overweight, injury, or overuse.

Who does OA affect?

Twenty-seven million people are affected by OA in the United States alone.2 Although OA can affect anyone at any age, it has been linked to the aging process. More than 50% of everyone over 65 has OA symptoms in one or both knees. By 75, virtually everyone suffers with OA in one or more joints. In fact, OA of the knee and hips continues to be the most common cause of arthritis-related disability for Americans. The Arthritis Foundation cites that OA most commonly affects middle-aged and older people, with most people getting it after age 45. Men under age 55 are more likely to have OA than women under 55. After age 55, women are more commonly affected, and overall, more women have OA than men.2

What are the symptoms of OA?

Although some people who have OA say they feel no pain, most people who have OA experience pain, feel joint stiffness (especially in the morning), show signs of swelling and tenderness in one or more joints and may even hear a crunching sound in their joints. For some people, OA can become completely debilitating.

In order to diagnose you properly, your doctor will consider your symptoms and your medical history, examine your joint(s), and order one or more diagnostic tests. Your doctor may order blood work, X-rays, a CT scan, or an MRI to get a clear view of the alignment of your painful joint and its condition.

How is OA treated?

Look at the big picture.

Your doctor may recommend different treatment options depending on the severity of your OA and its impact on your joint(s).

Your doctor may recommend that you lose weight, take certain nutritional supplements, and exercise. In some cases, a physical therapist may help provide pain relief and the return of some lost mobility through guided exercise and other techniques.

Manage the pain.

Your doctor may prescribe or recommend the use of anti-inflammatory medications (like aspirin or ibuprofen) and cold packs, which may help to reduce inflammation as well as the pain associated with arthritis. Sometimes a local injection of cortisone helps to further reduce inflammation.

Get the right support.

Orthotic devices sometimes help. Custom-made shoes and shoe inserts provide support for those with OA in the foot or ankle. Your doctor may recommend a brace or a cane to help take some of the pressure off your affected joint while you walk if OA is affecting your knee or hip.

Understand your surgical options.

If you are still experiencing arthritis pain and joint damage that's affecting your quality of life even after all other conservative measures have been taken, your doctor may suggest surgery to help relieve your pain and increase your mobility. Your doctor will determine the proper surgical treatment based on the severity of your arthritis and its location. Today, a full range of surgical solutions exists that enables your doctor to tailor surgical procedures to your particular needs and anatomy, whether you need arthroscopic debridement (removing inflamed and/or irritating debris from the joint), arthrodesis (fusing the joint for greater support), or arthroplasty (replacing the arthritic joint).

Be sure to talk with your doctor about the best treatment option for you.


  1. Arthritis Foundation. Arthritis facts. Accessed October 1, 2008.
  1. Arthritis Foundation. Osteoarthritis. Accessed October 1, 2008.

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