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 The Australian authors say the link between parents and adult
children shows that genetics may have much to do with knee problems
and the pain that goes with them.
“It was abundantly clear that genes were a strong contributor to
risk of osteoarthritis but there had been limited success in finding
these genes,” said Dr. Graeme Jones of the University of Tasmania in
Hobart, the study’s senior author.
“Thus, a better way may be to look at mechanisms by which genes lead
to arthritis and the best way of doing this was to study the adult
children of people who have had knee replacements for
osteoarthritis,” Jones told Reuters Health in an email.
By age 45, about one-quarter to one-third of adults have had knee
pain that lasted for at least one week, the study authors write in
the Annals of the Rheumatic Diseases .
The causes of knee pain aren’t always clear, but previous studies
have also suggested a genetic link.
The new study is the first to examine whether people who have a
family history of osteoarthritis of the knee have a greater risk of
worsening knee pain, according to the authors.
They enrolled 186 adults with at least one parent who had knee
replacement surgery at one of the hospitals in Hobart, and an
additional 186 adults whose parents had no history of knee arthritis
or knee replacement surgery.
At the beginning of the study, participants answered questionnaires
reporting any knee pain they had experienced over the past year, and
had X-rays and MRI scans of their right knees. These measures were
all repeated two years later and again 10 years after the initial
enrollment.
The adults whose parents had knee replacement surgery tended to be
heavier and there were more smokers compared to the control group,
but there were no differences between the groups as far as visible
damage to the knee joints at the beginning of the study.
After two years both groups had about the same number of
participants with knee pain – just over half. But after ten years,
74 percent of the children of parents with knee replacements had
knee pain compared to 54 percent of those with no family history of
knee surgery.
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Over those eight years there was also an increase in total knee pain
in members of both groups, but the offspring of parents with knee
surgeries tended to have a greater increase in pain.
Even after accounting for actual structural problems in the
participants’ knees, the researchers found that offspring of people
with knee replacement surgery were 2.2 times as likely to report
that their pain had worsened compared to the controls.
“I suppose there are many mechanisms by which genes lead to
arthritis - some we can help, some we can’t,” Jones said. “Offspring
have more pain, weigh more, are more susceptible to the effects of
smoking, have weaker muscles, more splits in the cartilage and
menisci and greater cartilage loss over time."
Since differences in arthritis and other structural knee problems
did not explain the differences between groups in knee pain, Jones
said that genetics most likely accounted for the outcomes – for
instance, a greater sensitivity to pain that might be influenced by
genes.
Still, other factors, such as aspects of the environment, that were
shared by both parents and adult children could not be ruled out, he
said.
To avoid knee pain, Jones suggests that people maintain an ideal
body weight, minimize their risk of knee injury, exercise more when
they’re younger and refrain from smoking.
“Develop ways of decreasing pain severity, and manage stress
better,” he added. “Consider medications such as glucosamine if at
high risk.”
SOURCE: http://bmj.co/1zCnywT Annals of the Rheumatic Diseases,
online December 4, 2014.
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