Older adults with knee arthritis or other chronic knee pain may be at heightened risk of breaking a hip, a UK study suggests.

The risk, researchers found, does not stem from the higher rate of falls among people with knee problems. Instead, they may suffer more fractures because they tend to have more-severe falls, the study authors report in the journal Arthritis & Rheumatism.

The findings are based on a three-year study of 6,641 men and women age 75 and older. During that time, nearly 4,000 study participants suffered a fall, resulting in 436 fractures in areas other than the spine.

In all, men and women who had chronic knee pain at the study’s outset were twice as likely to break a hip as those without knee problems.

And though knee pain sufferers were more likely than their peers to suffer a fall, that didn’t explain their higher rate of bone fracture, according to the study authors, led by Dr. Nigel K. Arden of Southampton General Hospital.

Instead, the researchers suspect that older adults hobbled by knee pain are more likely to suffer the types of falls that put the hip bones at risk.

They base this, in part, on the fact that study participants with knee pain had no elevated risk of wrist fracture, which typically happens when a person lands on an outstretched hand to break a fall. Hip fractures, on the other hand, are more likely to occur when a person falls straight down or to the side, landing on the hip.

According to Arden’s team, people with knee pain may have been more vulnerable to this type of fall because they often used walking aids - making them more likely to fall straight down on the hip.

The findings, the researchers conclude, suggest that chronic knee pain should be considered “a strong risk factor for fractures.”

SOURCE: Arthritis & Rheumatism, August 15, 2006.