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Osteoarthritis (OA) of the knee is a chronic, progressive disease of the joint involving the breakdown of cartilage. It is one of the most common diseases affecting virtually everyone over the age of 70. About 20 million Americans have osteoarthritis serious enough to cause pain and limit activities of daily living.
OA is often the result of years of accumulated wear and tear on the joint. There are other factors that play a role in the development of OA including certain occupations (those that involve standing or working on hard surfaces, work that involves impact loading on the knees, etc.), obesity, abnormal joint alignment, sports injuries, and family history.
The process of OA development is fairly straightforward. Cartilage is the smooth gristle that covers the ends of long bones. It is responsible for both absorbing the shock to the joint as well as allowing normal range of motion.
With OA, the smooth cartilage becomes pitted and frayed. Cartilage becomes less elastic, less able to absorb impact, and more easily damaged by overuse or injury. Synovial fluid, which is the joint fluid produced in the normal joint by the cells that line the joint, loses its cushioning and lubricating properties.
Large areas of cartilage can wear away so bones scrape over each other and cause pain.
Cartilage breakdown may cause the joint to lose its normal shape. Bone ends thicken and form bony spurs where the ligaments and joint lining attach to the bone.
Bits of cartilage, called joint mice, float around in the joint space causing further damage and pain.
So what are the treatment options?
OA is not curable yet but it is manageable. It is possible to treat OA so there is less stiffness and pain.
Key treatments include weight loss (if indicated), physical therapy, and anti-inflammatory medications. Occasionally steroid injections or injections of viscosupplements (lubricants) into the knee are helpful.
Ice (cold packs) and quadriceps strengthening exercises are also important in reducing pain.
Arthroscopy, a procedure where a small telescope is inserted into the knee and damaged or diseased tissue is removed, may be helpful in certain cases.
Bracing of the knee to help unload the narrowed compartment of the knee are very useful. These braces actually open up the narrowed compartment and ensure that a patient can walk with less pain. Coupled with arthroscopy and viscosupplementation, they may be extremely useful for relieving symptoms.
Wedge insoles in the shoes may help by partially correcting the alignment problem in the knees.
Finally in patients where all conservative measures have been exhausted, surgical correction in the form of total knee replacement may be required.
New data though shows that osteoarthritis probably begins earlier, probably in the second decade, in many patients.
Dr. Ewa Roos, professor in the Institute of Sports Science and Clinical Biomechanics of the University of Southern Denmark, presented an intriguing paper outlining her research. In it she described two populations of patients who suffer from osteoarthritis of the knee. The first group was comprised mainly of older women. The other group, though, consisted of men in their 30's and 40's (Roos EM, et al. Arthritis Rheum 2005; 52: 3507-3514).
A major hurdle to early diagnosis is that many younger patients with symptoms will have negative imaging studies… in other words, x-rays and magnetic resonance imaging (MRI) tests will be normal.
To complicate matters, patients who have x-ray evidence of osteoarthritis don't necessarily have symptoms.
Risk factors that are common to people with osteoarthritis are genetic predisposition and excessive weight.
In addition, patients who have suffered knee injuries to the anterior cruciate ligament (ACL) and menisci- the cartilage cushions in the knee- are also at increased risk for developing OA (Englund M, et al. Arthritis Rheum 2007; 56:4048-4054).
In related studies, it has been shown that regular exercise is both protective and preventative as far as osteoarthritis of the kb nee is concerned.
In other words, exercise appears to strengthen joint cartilage in patients with OA of the knee. Measurements of glycosaminoglycans, a measure of strength and elastricity in the joint, showed significant improvements in the knees of patients with OA who regularly exercised compared to control subjects who did not.
Many patients with OA of the knees are resistant to the idea of exercise since they feel it may cause the joints to wear down even faster. The results of the above studies clearly indicate that exercise should be encouraged.
For symptomatic relief, strengthening and stretching exercises accompanied by the judicious use of ice and anti-inflammatory medications may be quite helpful.
In the past, corticosteroid (“cortisone”) injections were routinely prescribed for patients with moderate to severe pain from OA. However, evidence indicating that corticosteroids ultimately cause cartilage to wear away faster than it should, has concerned physicians to the point where these injections are used less.
Viscosupplements, lubricants that help the knee to glide better, and which may help slow down the process of wear and tear are helpful for some patients.
More recently, the use of autologous stem cell therapy (stem cells harvested from the patient himself) has shown great promise, not only for symptomatic relief but for actual reversal of cartilage wear and tear with possible re-growth of cartilage. For more information about this procedure, contact the Arthritis and Osteoporosis Center of Maryland at (301) 694-5800.
Total joint replacement is reserved for those patients in whom conservative measures have failed.