Abstract
ObjectiveTo identify the prevalence of and risk factors for knee pain and radiographic knee osteoarthritis (RKOA) and to investigate the relationship between decreased lower extremity muscle mass (DLEM) and knee pain severity.MethodsUsing data from the Korea National Health and Nutrition Examination Survey, 3,278 participants who were ≥50 years old and who underwent dual x-ray absorptiometry, plain knee radiographs and completed a knee pain questionnaire were enrolled. Lower extremity muscle mass (LEM) was defined as the sum of the fat-free soft tissue mass of the legs, and lower extremity muscle mass index (LMI) was calculated as LEM/body weight (%). DLEM was defined as an LMI more than two standard deviations below the mean of a gender-matched young reference group. Categorical variables were presented as numbers (weighted %).ResultsThe prevalence of knee pain and RKOA were 22% (n = 721) and 34.7% (n = 1,234), respectively. Multivariate logistic regression analysis showed being female (OR 2.15, 95% CI 1.67–2.79), older (OR 1.03, 95% CI 1.01–1.04), less educated (OR 1.72, 95% CI 1.09–2.71), stiffness (OR 16.15, 95% CI 12.04–21.66), bed rest (OR 2.49, 95% CI 1.81–3.43), RKOA (OR 2.20, 95% CI 1.78–2.74) and DLEM (OR 1.54, 95% CI 1.09–2.17) were associated with knee pain. Participants with simultaneous RKOA and DLEM complained of more severe pain (pain score 7.18 ± 2.48) than those with knee pain without RKOA or DLEM (5.02 ± 2.44), those with only RKOA (6.29 ± 2.50), or those with only DLEM (6.78 ± 2.18) (P<0.001). These results remained after multivariate analyses of variance (MANOVAs).ConclusionThe prevalence of knee pain and RKOA were 22% and 34.7%, respectively, in the general Korean population. DLEM was an independent risk factor for knee pain and it was associated with increased pain severity, regardless of RKOA.
Highlights
The number of elderly people in the world is increasing
Multivariate logistic regression analysis showed being female, older, less educated, stiffness, bed rest, radiographic knee osteoarthritis (RKOA) and decreased lower extremity muscle mass (DLEM) were associated with knee pain
DLEM was an independent risk factor for knee pain and it was associated with increased pain severity, regardless of RKOA
Summary
The number of elderly people in the world is increasing. With aging, chronic pain, especially knee pain, is becoming a serious social problem, causing impairments in physical function and quality of life, as well as increased morbidity. Previous studies have revealed multifactorial risk factors for knee pain, including obesity, radiographic changes, female gender, older age, stiffness and previous knee injury, the underlying etiology for knee pain remains poorly understood [1,2,3,4]. Well-known risk factors for knee pain in patients with knee OA are old age, female gender, and obesity [9]. Another strong risk factor involves radiographic changes. Radiographic change, but additional aggravating factors might be related to knee pain severity in patients with osteoarthritis [8, 13]
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