More older Americans have knee pain, replacement

Older Americans are increasingly complaining of aching knees, and getting those knees replaced, even though X-ray evidence of knee arthritis is not on the rise, a new study finds.

Since the 1970s and 1980s, the percentage of older Americans reporting chronic knee pain has risen as much as three-fold - both among people with visible signs of arthritic joints and those without any apparent arthritis.

Despite stable rates of knee arthritis, knee replacement surgeries rose almost nine-fold in 26 years, researchers report in the Annals of Internal Medicine.

The nation's growing obesity problem and an aging population seemed to partly account for the increase in knee pain, the study found. But that did not tell the whole story.

"We don't really know what the other reasons could be," said lead researcher Uyen-Sa D.T. Nguyen, of Boston University School of Medicine.

One possibility, she told Reuters Health, is that older adults these days are more likely to admit to having pain.

Knee pain facts

The knee joint has three compartments: medial, lateral, and patellofemoral.
Causes of knee pain include injury, degeneration, arthritis, infrequently infection, and rarely bone tumors.
Ligaments within the knee (cruciate ligaments) and on the inner and outer sides of the knee (collateral ligaments) stabilize the joint.
Surgical repair of ligament injury can involve suturing, grafting, and synthetic graft repair. Some patients require total knee replacement.
Routine X-rays do not reveal meniscus tears but can be used to exclude other problems of the bones and other tissues. Arthroscopy and MRI studies are used most frequently to diagnose knee ailments; occasionally, a needle aspiration of fluid is done.
The knee joint is one of the most commonly involved joints in rheumatic diseases (over 100 disease types). Rheumatic diseases are immune diseases that affect various tissues of the body, including the joints, by causing arthritis (pain, swelling, stiffness, and limited joint movements).

"I suspect that what happened in the past is that people often wouldn't complain," agreed senior researcher Dr. David T. Felson, who is also with Boston University.

But it's hard to know for sure, the researchers say.

Regardless, it's possible that the rising rate of knee pain is one factor in the surge in knee replacement surgeries in recent decades, Felson said.

Knee replacement is one treatment option for severe osteoarthritis - the "wear-and-tear" form of arthritis, in which cartilage cushioning the joints gradually breaks down. That allows bones to rub together, which can cause pain, swelling and limited range of motion. Over time, the joint may become permanently misshapen.