Squatting posture increases prevalence of knee OA

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Rheumawire

Apr 22, 2004

Squatting posture increases prevalence of knee OA

Boston, MA and Beijing, China - The latest data from US and Chinese

researchers in the Beijing Osteoarthritis Project show that squatting, a

common daily posture in China, accounts for much of the increased

prevalence of knee osteoarthritis (OA) in Chinese vs American subjects.

Dr Yuqing Zhang reports in the April 2004 issue of Arthritis &

Rheumatism that the prevalence of tibiofemoral OA increased with greater

time spent squatting in both male and female Chinese subjects [1].

" These results may explain, in part, why the Chinese elderly subjects,

especially the women, had such a high prevalence of knee OA, even though

they were thinner than the white subjects from the US, " Zhang writes.

Zhang and colleagues at Boston University School of Medicine, the

University of California, San Francisco, and Peking Union Medical

College Hospital, Beijing, examined the association between squatting

and the prevalence of radiographic OA in different knee compartments.

They recruited a random sample of 755 men and 1103 women in Beijing and

compared them with white subjects in the Framingham, MA cohort.

" Nonoccupational squatting is a common posture in daily living among

Chinese men and women, and this phenomenon is also prevalent in other

Asian countries. Thus, Asian populations provide a unique opportunity to

assess the effect of squatting during daily living on the risk of knee

OA, " Zhang says.

All subjects were >60 years and were interviewed at their homes by

trained health professional interviewers. The standardized questionnaire

included joint symptoms, previous diagnoses of arthritis, and OA risk

factors, as well as asking subjects to recall how much time they spent

squatting per day, on average, at age 25 years. Clinical evaluation at

Peking Union Medical College Hospital included height, weight,

quadriceps strength, bone-mineral density, and anteroposterior (AP)

radiograph of both knees with the knee joints fully extended and in a

weight-bearing position and a weight-bearing skyline view.

The Chinese subjects were on average thinner than their elderly white

counterparts. Zhang reports that after adjusting for age and other risk

factors, in comparison with men who reported squatting <30 minutes per

day, there was a 70% increased risk of tibiofemoral OA in those

squatting 120 to 179 minutes per day, and almost double risk in those

who squatted >180 minutes per day.

Zhang reports that the effect of squatting was greater for medial

tibiofemoral OA than for lateral tibiofemoral OA in men but squatting

increased the risk of both types of OA in women. The investigators

suggest that this might be due to differences in knee stability or

stiffness, which is reduced in women as a result of decreased

neuromuscular strength and increased ligamentous laxity.

Squatting also increased the risk of patellofemoral OA, but the effect

was less than on tibiofemoral OA.

Janis

Source

1. Zhang Y, Hunter DJ, Nevitt MC, et al. Association of squatting with

increased prevalence of radiographic tibiofemoral knee osteoarthritis:

the Beijing Osteoarthritis Study. Arthritis Rheum 2004 Apr;

50(4):1187-92.

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