The Survey of Knee Osteoarthritis in the Population over Age 50 Visited in the Health Bus in Kermanshah, Iran

Along with an aging population worldwide, knee osteoarthritis (KOA), which is the main cause of musculoskeletal pain and disability in the elderly and decreases the quality of life, is prevalent, and their impact is widespread. This study aimed to evaluate the knee osteoarthritis status among the population over age 50 in Kermanshah, Iran. The research community consisted of the population who has been visited in the health bus in Kermanshah in 2016-2017, of which 589 were chosen by an available sampling method. A WOMAC questionnaire was used to determine the prevalence of knee osteoarthritis. The prevalence of knee stiffness rate after sitting, lying down, or resting during the day among women and men were 40.7% and 20.5%, respectively. According to the findings, the highest prevalence rate of knee pain was in subjects with a BMI higher than 30 (31.6%) and BMI 25–30 (24.5%). 39.2% of the subjects never experienced knee pain, 16.6% monthly, 13.4% once a week, 20.4% daily, and 10.4% of them had prolonged knee pain experience. The prevalence of gender-based knee pain was 60.5% among women and 38.6% among men. 30.5% of women and 61.4% of men never experienced knee pain.


Introduction
Along with an aging population worldwide, the pattern of disease prevalence has changed from acute infectious diseases to chronic noncommunicable diseases such as chronic musculoskeletal disorders. Musculoskeletal disorders are prevalent, and their impact is widespread [1]. ey are the most prevalent cause of severe and prolonged pain and physical disabilities, and they have affected hundreds of millions of people worldwide and are considered a global health concern [2,3].
One of the common musculoskeletal disorders is knee osteoarthritis (KOA), which is the main cause of musculoskeletal pain and disability in the elderly. It decreases the quality of life [4]. is problem often results in severe side effects, and in the second half of the life, it costs the heavy burden of treatment. Knee osteoarthritis includes the degeneration of cartilage with pain inside and around the knee joint, as well as joint stiffness, and decreased range of motion, which ultimately leads to muscle weakness and is the biggest cause of functional disability [4].
Generally, the first symptom of KOA is joint pain, and in patients aged over 55 years, knee pain is often associated with osteoarthritis. Nearly 25% of adults aged over 55 have experienced knee pain at least once a year, which probably is a sign of underlying KOA [4][5][6][7].
KOA affects 80% of the elderly and 27 million people in the United States each year, and their treatment costs are $ 185.5 billion annually [6]. e prevalence of this disease is expected to rise the given ever-aging population and the fact that obesity is becoming increasingly common, for example, the prevalence of KOA in Sweden is projected to increase from 13.8% in 2012 to 15.7% in 2032 [5,8,9]. e prevalence of KOA in the Asia-Pacific region is 7.50%. is is 5.78% in China, 12.4% in South Korea, 22.0% in rural India, 25.00% in rural population of North Pakistan, and 10.2% in Bangladesh [8,[10][11][12][13][14]. Besides aging and obesity, gender, physical activity level, genetic predisposition, and injury are also risk factors of KOA [4]. Considering that the age-related burden of disease such as osteoarthritis will be significantly accelerated among developing countries, osteoarthritis prevalence will rise, particularly in Asian countries in the future [15].
Mobility and having a painless limb are crucial to perform daily regular activities. e health of the musculoskeletal system is an important part of health. With aging, many issues occur in this motor system. erefore, particular attention to the physical health and the motor system in a macrolevel society is important as an infrastructure for development. Hence, this study aimed to evaluate the prevalence of KOA as one of the most common problems in the musculoskeletal system among the population over age 50 as an indicator of physical health status in Kermanshah (a city in the west of Iran).

Materials and Methods
is cross-sectional descriptive study was conducted in 2016-2017. e research community consisted of the population over the age of 50, voluntarily visiting the health bus (a bus that was traveling throughout the city to collect health information) in Kermanshah.
e sample size of the present study calculated 588 subjects based on the WHO-ILAR COPCORD study in Sanandaj [16], with a 95% confidence interval, the accuracy of 4%, and prevalence of 42.8% complaints of musculoskeletal pain in the past 7 days. e inclusion criteria for entering this study were aged over 50 years and the individual's desire to be involved in the study. e sampling of the present study was carried out in a gradual method until the samples were accomplished. According to the division of urban areas, the residential areas in the city were divided into eight municipal districts, and according to the schedule, each week, the evaluation bus traveled to one of the neighborhoods and was located in each neighborhood for one week. e bus designed for this purpose had the facilities for collecting data and was located at the centre of the neighborhood, with posters, fliers, and placards announcing that the bus welcomed volunteered participants to be evaluated.
Regardless of having knee pain, those who volunteered to be assessed on the bus, in addition to overall health assessment, their condition of the musculoskeletal system was also assessed, and Western Ontario and McMaster Universities Osteoarthritis Index questionnaire (WOMAC) was completed for them.
Western Ontario and McMaster Universities Osteoarthritis Index questionnaire (WOMAC) was used to assess the status of people in terms of the KOA. e questionnaire includes 17 questions about functional activities, 5 questions about painful activities, and 2 questions about joint stiffness. In the study conducted by Ebrahimzadeh and colleagues in 2014, this questionnaire was translated into Persian, and psychometric evaluation has been performed. In this study, Cronbach's alpha was 0.917, which showed high internal consistency of the questionnaire as a reliable tool. Intercorrelation matrix between different scales of the WOMAC Persian questionnaire version showed a high correlation between the subscales of stiffness, pain, and physical function. In addition, this study showed that the WOMAC Persian index is a valid and reliable clinical tool for reporting KOA [17]. Finally, after completing the questionnaire by a questioner (researcher), the data were analyzed by the SPSS software version 18 and expressed using descriptive statistics.

Results.
e results of the recent study showed that about 72% of the participants were women. 67% of the samples were housewives. Furthermore, 35% of them had a BMI over 30 (Table 1).
According to the results of the WOMAC, the prevalence of knee pain among the studied samples was 60.8%. Meanwhile, 39.2% of the subjects never experienced knee pain, 16.6% had monthly, 13.4% once a week, 20.4% on daily basis, and 10.4% of them had prolonged knee pain experience. e results of Section 1 of the knee questionnaire are given in Table 2.
e prevalence of knee pain when doing activities such as going up and downstairs, sitting, and lying down is given in Table 3. e prevalence of knee stiffness immediately after morning wake-up was 33.3% among participants. Furthermore, the prevalence of knee stiffness after sitting, lying down, or resting during the day was 35% (Table 4).
According to the data, the prevalence of gender-based knee pain was 60.5% among women and 38.6% among men. 30.5% of women and 61.4% of men never experienced knee pain. 19.1% of women and 10.2% of men once a month, 13.0% of women and 14.5% of men once a week, 23.6% of women and 12.0% of men daily, and 13.7% of women and 1.8% of men had prolonged knee pain experience (Table 5). Table 6 is hyperlinked and could be accessed to address the prevalence of gender-based knee pain through the various activities between men and women. e findings indicated that the prevalence of knee stiffness immediately after morning wake-up based on gender was 38.3% among women participants and 19.3% among men. e knee stiffness prevalence rate after sitting, lying down, or resting during the day was 40.7% among women and 20.5% among men.
According to the findings of the present study, the high prevalence of daily and prolonged knee pain was recognized among housewives ( Figure 1). e results presented in Table 7, hyperlinked and could be read, indicated that according to the findings, the highest prevalence of knee pain was in subjects with BMI higher than 30 (31.6%) and BMI 25-30 (24.5%). e lowest prevalence of knee pain was seen in subjects with lower BMI than 18.5 (1%) ( Table 7). e prevalence of knee stiffness associated with the BMI of the studied participants is given in Table 7.

Discussion.
Considering the importance of prevention and early treatment of KOA and providing appropriate guidelines in order to prevent it, this study aimed to evaluate the KOA status among the population over age 50 in Kermanshah.
e results of the study showed that the prevalence of knee pain in the samples was 60.8%.      e data of the present study indicated that the KOA symptoms increase with age. In a demographic study in urban and rural areas of Bangladesh, the similar findings with age were seen [13]. e results presented in Table 7 provide that the highest prevalence rate of knee pain was in subjects with BMI higher than 30 (31.6%) and BMI 25-30 (24.5%). e lowest prevalence of knee pain was seen in subjects with lower BMIs than 18.5 (1%). e results of Qing Yu and colleagues indicated a strong association between high BMI and the risk of KOA. In the study of Qing yu and colleagues, BMIs were higher in the group with KOA than in the group without KOA, which is aligned with the current research [6]. Some studies consider female gender as one of the risk factors for knee pain and KOA [18][19][20]. It was seen in the present study that the prevalence of musculoskeletal disorders is higher in women than men. Of course, it is noteworthy that the number of women participating in the study was more than men, which may be due to men's employment and business when the bus was accepting patients and their lack of opportunity to visit the bus.
e study results of the Haq and colleagues also indicated a high prevalence of osteoarthritis among women [13]. e study by Zeng and colleagues in China showed that the prevalence of KOA was higher among women than men [6]. Research results in Australia also indicated that the prevalence of osteoarthritis among women is higher than men [21].
Studies have revealed that some occupational physical activities can increase the risk of osteoarthritis [22][23][24]. In the present study, knee pain was higher among housewives than other participants in the study. e findings of Dahaghin and colleagues study also indicated that housewives are more prone to KOA than women working outside [25].
Of course, less muscle mass in women than men can also have more impact on their functional limitations along with    [26] that can lead to a high prevalence of knee pain among housewives, which needs more investigations. e study conducted by Ricci and colleagues showed that arthritis is prevalent in workers aged 40-65. e findings of our study also showed that after housekeeping, workers had the most experience with knee pain among other studied occupations. However, knee pain experience was for less than half of the workers. Of course, this may be due to the small number of workers participating in the study [24].

Conclusions
e prevalence of knee pain in the population over the age of 50 who participated in the study was high. Knee pain and stiffness were more prevalent in women than men. e high prevalence of this problem was recognized among housewives and subjects with BMI higher than 30.
Data Availability e datasets used and/or analyzed during the current study are available from the corresponding author upon request.

Conflicts of Interest
e authors declare that they have no conflicts of interest.

Authors' Contributions
Mohammad Bagher Shamsi contributed to original idea and protocol, the conception of the work, conducting the study, revising the draft, approval of the final version of the manuscript, and agreed for all aspects of the work. Ameneh Safari contributed to the design of the work and revising the draft and approval of the final version of the manuscript. Ali Soroush contributed in conception of the work, editing of this manuscript, and approval of the final version of the manuscript. Yahya Safari involved in data analysis, drafting of the manuscript, and approval of the final version of the manuscript. All authors provided their consent for this publication.