Knee replacement operations on older adults have risen 162% in the last 20 years, a new study finds. Many had to be repeated. Second operations such as these doubled. Medicare spends about $15,000 on each knee replacement. All of these numbers will only go up as baby boomers get older. Researchers used Medicare data for their study. Medicare patients had 243,802 knee replacements in 2010. There were 93,230 in 1991. Some people needed "revisions," or second surgeries. The number of these procedures doubled, from 9,650 to 19,871. The average hospital stay for knee replacement was cut in half during these two decades. But there were more problems afterward for people who had revision surgeries. They were twice as likely to need a second hospital stay after surgery as patients in 1991. The Journal of the American Medical Association published the study September 26. USA Today and HealthDay News wrote about it.

By Robert H. Shmerling, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

I often have to tell my patients with arthritis something they don't want to hear: You need joint replacement surgery.

This is never welcome news. After all, joint replacement is a big deal. There are the usual risks of an operation, such as bleeding or infection. Recovery and rehabilitation can take months. But it's usually worthwhile. Up to 90% of people who have joint replacement consider it a success.

When things go well, total joint replacement reduces pain dramatically. That allows better function and a better quality of life. In fact, many of my patients who finally have joint replacement surgery tell me they wish they'd had it sooner.

A common reason for joint replacement surgery is advanced osteoarthritis. This is the "wear-and-tear" type of joint damage that tends to occur with aging. Surgery is often needed because no treatments have been discovered to slow down or reverse this damage. The knee and hip are the joints most commonly replaced.

A new study looks at trends in total knee replacement among more than 3 million people on Medicare. Their average age was about 75. The study also included more than 318,000 people who had a "revision" joint replacement. This is replacement for a joint that's been replaced before.

Between 1991 and 2010:

• The number of people having total knee replacement each year nearly tripled (from about 93,000 to almost 244,000).
• The yearly number of knee replacements for each 10,000 people on Medicare doubled, from 31 to 62.
• The number of revision total knee replacements each year more than doubled, from 9,650 to 19,871.
• Returns to the hospital after total knee replacement increased. So did infection rates after revision surgery.

These findings translate into some impressive costs. Total knee replacements cost an average of $15,000. So Medicare is spending more than $3.6 billion each year just on total knee replacements.

I think there are several reasons for the growth in total joint replacements. They include:

• An expanding population of older adults, since osteoarthritis rates increase with age.
• Better health among the aged, which makes them better candidates for surgery.
• A rise in obesity, which increases the risk of osteoarthritis.

Orthopedic surgeons also may be offering surgery to people they would have turned down in the past. Obesity and other medical problems increase the risks of problems after surgery. But the safety of this operation and the anesthesia for it have improved. So surgeons may consider more people to be good candidates for joint replacement.

There's support for this idea in the new study. Obesity rates among those having knee replacement surgery increased from 4% to 11.5%. Problems after surgery that led to a new hospital stay also rose. This suggests an increase in higher risk patients.

What Changes Can I Make Now?

You may be able to reduce your risk of osteoarthritis. Here are some things you can do:

• Lose excess weight. Obesity is linked with a higher risk of osteoarthritis. The likely reason is that it places more than normal stress on weight-bearing joints.
• Take steps to prevent injuries, such as fractures or ligament tears. For example, wear protective gear and train properly for athletic activities. Sports injuries can lead to osteoarthritis.
• Get treatment for other joint diseases. A good example is rheumatoid arthritis. This disease causes long-term inflammation that damages joints. Taking medicines to control the disease can reduce the risk of osteoarthritis in the future.

If you already have osteoarthritis, treatments include:

• Mild pain relievers, such as acetaminophen (Tylenol and others) or nonsteroidal anti-inflammatory drugs (such as ibuprofen and naproxen)
• Strong pain relievers, such as tramadol (Ultram) or codeine-type medicines
• Injections of a corticosteroid drug into the joint
• Hyaluronate injections -- This is a synthetic lubricant approved for osteoarthritis of the knee.
• Glucosamine, with or without chondroitin -- This supplement may provide relief for mild pain.
• Treatments applied to the skin (such as capsaicin)
• Heat or cold applied to the painful joint
• Exercise -- Talking to a physical therapist may help. He or she can assess your joint health and design an exercise program for you.

Surgery is usually reserved for people who have:

• Severe pain that is not relieved by other treatments
• Declining function (such as impaired walking)
• X-ray evidence of severe arthritis
• Good general health (so that surgery is not considered too risky)

What Can I Expect Looking to the Future?

The U.S. population is becoming older and more obese. This will likely lead to more osteoarthritis. So you can expect the number of knee replacements to rise even further. Of course, costs will rise, too. I hope that surgical techniques will continue to improve so that fewer revisions will be needed.

Some may wonder whether all of these operations are necessary. I would not be surprised if health insurance companies make increased use of criteria to decide when to cover joint surgeries.