There are some 100 different forms of arthritis,1 rheumatic diseases, and related conditions. Virtually all of them have the potential to affect the knees in some way; however, the following are the most common.
- Osteoarthritis. Some people with knee problems have a form of arthritis called osteoarthritis. In this disease, the cartilage gradually wears away and changes occur in the adjacent bone. Osteoarthritis may be caused by joint injury or being overweight. It is associated with aging and most typically begins in people age 50 or older. A young person who develops osteoarthritis typically has had an injury to the knee or may have an inherited form of the disease.
- Rheumatoid arthritis. Rheumatoid arthritis, which generally affects people at a younger age than does osteoarthritis, is an autoimmune disease. This means it occurs as a result of the immune system attacking components of the body. In rheumatoid arthritis, the primary site of the immune system’s attack is the synovium, the membrane that lines the joint. This attack causes inflammation of the joint. It can lead to destruction of the cartilage and bone and, in some cases, muscles, tendons, and ligaments as well.
- Other rheumatic diseases. These include:
- Gout. An acute and intensely painful form of arthritis that occurs when crystals of the bodily waste product uric acid are deposited in the joints
- Systemic lupus erythematosus (lupus). An autoimmune disease characterized by destructive inflammation of the skin, internal organs, and other body systems, as well as the joints
- Ankylosing spondylitis. An inflammatory form of arthritis that primarily affects the spine, leading to stiffening and in some cases fusing into a stooped position
- Psoriatic arthritis. A condition in which inflamed joints produce symptoms of arthritis for patients who have or will develop psoriasis
- Infectious arthritis. A term describing forms of arthritis that are caused by infectious agents, such as bacteria or viruses. Prompt medical attention is essential to treat the infection and minimize damage to joints, particularly if fever is present.
Symptoms of Knee Arthritis
The symptoms are different for the different forms of arthritis. For example, people with rheumatoid arthritis, gout, or other inflammatory conditions may find the knee swollen, red, and even hot to the touch. Any form of arthritis can cause the knee to be painful and stiff.
Diagnosis of Knee Arthritis
The doctor may confirm the diagnosis by conducting a careful history and physical examination. Blood tests may be helpful for diagnosing rheumatoid arthritis, but other tests may also be needed. Analyzing fluid from the knee joint, for example, may be helpful in diagnosing gout. X rays may be taken to determine loss or damage to cartilage or bone.
Treatment of Knee Arthritis
Like the symptoms, treatment varies depending on the form of arthritis affecting the knee. For osteoarthritis, treatment is targeted at relieving symptoms and may include pain-reducing medicines such as aspirin or acetaminophen; nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen; or, in some cases, injections of corticosteroid medications directly into the knee joint. Other treatments for the pain of knee osteoarthritis include injections of hyaluronic acid substitutes and the nutritional supplements glucosamine and chondroitin sulphate.
People with diseases such as rheumatoid arthritis, ankylosing spondylitis, or psoriatic arthritis often require disease-modifying antirheumatic drugs (DMARDs) or biologic response modifiers (biologics) to control the underlying disease that is the source of their knee problems. These drugs are typically prescribed after less potent treatments, such as NSAIDs or intra-articular injections, are deemed ineffective.
DMARDs are a family of medicines that may be able to slow or stop the immune system from attacking the joints. This in turn prevents pain and swelling. DMARDs typically require regular blood tests to monitor side effects. In addition to relieving signs and symptoms, these drugs may help to retard or even stop joint damage from progressing. However, DMARDs cannot fix joint damage that has already occurred. Some of the most commonly prescribed DMARDs are methotrexate, hydroxychloroquine, sulfasalazine, and leflunomide.
Biologic response modifiers, or biologics, are a new family of genetically engineered drugs that block specific molecular pathways of the immune system that are involved in the inflammatory process. They are often prescribed in combination with DMARDs such as methotrexate. Because biologics work by suppressing the immune system, they could be problematic for patients who are prone to frequent infection. They are typically administered by injection at home or by an intravenous infusion at a clinic. Some commonly prescribed biologics include etanercept, adalimumab, infliximab, and anakinra.
People with any type of arthritis may benefit from exercises to strengthen the muscles that support the knee and from weight loss, if needed, to relieve excess stress on the joints.
If arthritis causes serious damage to a knee or there is incapacitating pain or loss of use of the knee from arthritis, joint surgery may be considered. Traditionally, this has been done with what is known as a total knee replacement. However, newer surgical procedures are continuously being developed that include resurfacing or replacing only the damaged cartilage surfaces while leaving the rest of the joint intact.
Last Updated April 19, 2012