RESEARCH - Risk of knee OA twice as high in siblings

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Risk of knee OA twice as high in siblings

Rheumawire

Sep 1, 2004

Mann

Nottingham, UK - Risk of knee osteoarthritis (OA) is twice as high among

siblings of patients with severe knee OA as among the general

population, according to a new sibling study by Dr RL Neame (City

Hospital, Nottingham, UK) and colleagues, published in the September

2004 issue of the ls of the Rheumatic Diseases [1]. " This is the

first large sibling study of knee OA and adds to the growing body of

evidence that there is a genetic contribution to common forms of OA, "

Neame writes. " Identification of the responsible genes will enhance our

understanding of OA pathogenesis. "

The sibling study assessed OA risk among 490 knee OA patients who

underwent total knee replacement (TKR) and 737 of their siblings aged

>40 years and 1729 community subjects aged >40 years with knee pain who

were recruited from neighboring family-doctor-practice lists. X-rays

were taken of the knees to look for evidence of structural changes

caused by osteoarthritis.The age-, sex-, and knee-pain adjusted odds

ratios in siblings were 2.9 for tibiofemoral OA and 1.7 for

patellofemoral OA. These findings held even after adjustment for such

knee OA risk factors as age, sex, body mass index, smoking, presence of

Heberden's or Bouchard's nodes, and meniscectomy

Overall, the study found that 62% of disease variance is likely

determined by hereditary. Knee OA heritability was 78% in men and 49% in

women.

The new heritability estimates are greater than previous estimates, and

the study authors note that this may explain why the overall finding was

higher than in a previous twin study that was restricted to women. In

that study, heritability accounted for 39% of knee OA risk [2]

The authors point out several cautionary notes about the study

conclusions, including the fact that aspects of shared family

environment such as sporting and leisure activities or diet were not

assessed. Moreover, only whites were included in the new report.

Finally, since the twofold increased risk is related to having a sibling

with severe OA, it cannot be generalized to those whose siblings have

milder disease.

Dr ph Seto (New York University School of Medicine, New York, NY)

believes that the findings will hold even with milder forms of OA.

" We certainly can see OA transmitted in families for anatomic and

biochemical reasons, " he tells rheumawire. " What is prudent if we do see

this pattern is to determine what the nature of the injury is and what

we can do to minimize susceptibility to knee OA. " The bottom line is

that knowing family history " can minimize risk and help patients avoid

knee OA, " he says.

Sources

Neame RL, Muir K, Doherty S and Doherty M. Genetic

risk of knee osteoarthritis: a sibling study. Ann Rheum Dis 2004;

63:1022-1027.

Spector TD, Cicuttini F, Baker J et al. Genetic

influences on osteoarthritis in women: a twin study. BMJ 1996;

312:940-943.

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org