Background/Purpose

knee osteoarthritis (OA) causes more limitations in physical function than other chronic conditions in Caucasians.  Knee OA is known to be more prevalent among Chinese than among Caucasians.  However, little is known about the effect of knee OA on physical function among Chinese living in rural areas. 

Methods

Wuchuan OA Study was a population-based cohort study conducted in the rural areas of Wuchuan, Inner Mongolia of China. Subjects completed a baseline home-interview in 2005, including knee symptoms and 8 physical function questions on daily-living activities (e.g., walking, going up or down stairs, bending or kneeling, chair standing, preparing meals, cleaning house, making beds, getting up bed) with 1: no difficulty, 2: some difficulty, 3: very difficult, and 4: unable to do.  Subjects had bilateral weight-bearing posterior-anterior and patellar skyline radiographs taken. Whole radiographic knee OA (ROA) was defined as either tibiofemoral K/L score≥2 or presence of patellofemoral OA. Symptomatic OA (SxOA) was defined as presence of both ROA and knee pain for most days in the last month. We identified distinct groups of limitation in physical function based on subject’s response to each of 8 physical function questions using a latent class model (SAS PROC LCA) and examined the relation of ROA and SxOA to the latent groups of limitation in physical function adjusting for potential confounders.

Results

Among 1025 subjects of Wuchuan OA study (men: 49.3%, mean age: 56.4 years, mean BMI: 22.4 kg/m²) prevalence of knee ROA and SxOA was 17.7% and 6.2%, respectively, at baseline. For KL grading, the weighted kappa for inter-rater reliability was 0.80 (95% confidence interval (CI): 0.72-0.88) and the intra-rater reliability was 0.92 (95% CI: 0.86-0.99).We identified 4 distinct physical function groups: no limitation (n=543, 53.0%), mild limitation (n=252, 24.6%), moderate limitation (n=128, 12.5%), and severe limitation (n=102, 9.9%). Worse limitation was characterized by increasing difficulty in performing 8 daily-living activities. The mean posterior probability of subgroup assignment was 0.90, suggesting a good-fit of model Compared with those without knee ROA, multivariable adjusted odds ratios (OR) of no, mild, moderate and severe limitation in physical function among subjects with ROA was 1.6 (1.0, 2.5), 1.9 (1.1, 3.3) and 3.3(1.9, 5.7), respectively. Association of SxOA with limitation in physical function was even stronger, with ORs being 1.0, 2.7, 3.6, and 11.3, respectively, for each increasing difficulty on activity limitations.    

Conclusion

Knee OA was strongly associated with limitation in physical function among people in rural areas of China. Knee OA is likely to become a major public health problem given the limitation in physical functioning associated with this disease among Chinese elderly.   

 

Knee OA Status	Limitations in Physical Function
	No	Mild		Moderate	Severe
No ROA (N=844)	57.2	24.2		11.6	7.0
ROA (N=181)	33.2	26.5		16.7	23.8
OR (95% CI)*	1.0	1.6 (1.0, 2.5)		1.9 (1.1, 3.3)	3.3 (1.9, 5.7)
No SxOA (N=962)	55.4		24.7	12.2	7.7
SxOA (N=63)	15.9		22.2	17.5	44.4
OR (95% CI)*	1.0		2.7(1.2, 6.3)	3.6 (1.5, 8.9)	11.3(4.9, 25.7)

*Adjusted for age, sex, BMI, years of education, annual income, physical activity, and number of comorbidities

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-of-knee-osteoarthritis-and-limitations-in-physical-function-in-a-rural-chinese-population-the-wuchuan-oa-study/