What is the prevalence of musculoskeletal problems in the elderly population in developed countries? A systematic critical literature review

Background The proportion of older people will be tripled by the year 2050. In addition, the incidence of chronic musculoskeletal (MSK) conditions will also increase among the elderly people. Thus, in order to prepare for future health care demands, the magnitude and impact of MSK conditions from this growing population is needed. The objective of this literature review is to determine the current prevalence of MSK disorders in the elderly population. Methods A systematic literature search was conducted in Pubmed on articles in English, published between January 2000 and July 2011. Studies from developed countries with prevalence estimates on elderly people (60+) on the following MSK conditions were included: Non-specific extremity pain, rheumatoid arthritis, osteoarthritis, osteoporosis, and back pain. The included articles were extracted for information and assessed for risk of bias. Results A total of 85 articles were included with 173 different prevalence estimates. Musculoskeletal disorders are common in the elderly population, but due to heterogeneity of the studies, no general estimate on the prevalence of MSK can be determined. Women report more often MSK pain than men. Overall, prevalence estimates either remain fairly constant or increase slightly with increasing age, but with a tendency to decrease in the oldest (80+) people. Conclusions Musculoskeletal disorders remain prevalent in the elderly population. Given the increasing proportion of elderly population in the world population and the burden of MSK diseases among the elderly people, efforts must be made to maintain their functional capacity for as long as possible through optimal primary and secondary health care.


Background
According to the United Nations (UN), the proportion of older people (i.e. aged 60 and over) will triple over the next 40 years and will account for more than 20% of the world's population by year 2050 [1]. In addition, it is estimated that one in five of the elderly population will be more than 80 years old in 2050. The exponential increase of elderly people is mainly due to a rise in life expectancy, especially in the developing countries. Along with the rise in the life expectancy there is also a rise in the incidence of non-communicable chronic conditions which again leads to increasing morbidity and disability [2]. According to the World Health Organization (WHO), one of the major disabling conditions among the elderly population is musculoskeletal (MSK) disorders [3,4]. The WHO has specifically identified four major disabling MSK conditions: osteoarthritis (OA), rheumatoid arthritis (RA), osteoporosis (OP), and back pain (BP) [4].
In 1998, the Bone and Joint Decade (BJD) 2000-2010 collaboration was initiated and endorsed by the UN and WHO, with the overall goal to reduce the burden and cost of MSK diseases [5,6]. In 2003, the WHO's Global Burden of Disease study and the Bone and Joint Monitoring Project conducted a large report on the burden of MSK disorders through the existing data on the four major MSK conditions (OA, RA, OP, and low back pain (LBP)) [4,5]. From this report, it is clear that the burden of these major MSK conditions increases with age.
From a health care perspective, the rising proportion and burden of older people demands that health care professionals increase their awareness of the health and disability of this particular population. Accordingly, there is a need to better understand the current magnitude and impact of MSK conditions from this growing population.
The aim of this paper is to estimate the current prevalence of musculoskeletal disorders in the elderly population by conducting a systematic literature review. Specifically, the objective was to estimate the prevalence of non-specific musculoskeletal pain, OA, RA, OP, and BP among older people in developed countries. Any methodological shortcomings will be discussed and future recommendations will be provided.

Definitions
Musculoskeletal pain in this review refers to the following five overall conditions: 1) non-specific MSK pain in the extremities, 2) RA, 3) OA, 4) OP (either spine or hip or a combination of both), and 5) BP (i.e. neck pain (NP), mid back pain (MBP), and LBP). The older population is defined as people aged 60 and over according to the UN's cut-off criterion [1]. The term "magnitude" in this review refers to the relative size (i.e. prevalence) of the selected MSK conditions. Hence, the quality of life, cost-of-illness, or social/personal burden of MSK disorders is not included. Developed countries are defined as countries with an advanced economy according to the International Monetary Fund, which includes 35 countries (Additional file 1) [7].

Search design
A systematic literature search was conducted in Pubmed (www.pubmed.org) and included studies published between January 1 st 2000 and July 1 st 2011. The timeperiod was chosen in order to only include studies published after the WHO reports [3,4]. Search terms included both free text and MeSH terms and were combined by Boolean terms (AND, OR, NOT) (Additional file 2). The following main terms were included: "musculoskeletal", "rheumatoid arthritis", "osteoarthritis", and "osteoporosis". The MeSH terms were limited to only include studies containing "epidemiology", "etiology", or "diagnosis". These were again combined with "prevalence", "cross-sectional studies". The search was limited by type of papers (review, government publications, technical reports or journal articles), age (MeSH terms: "aged" and "aged, 60 and over") and finally restricted to English language only. No additional search was conducted. The retrieval of potentially relevant articles was conducted in two phases by one examiner. The first phase focused on identifying relevant studies through Table 1 Inclusion and exclusion criteria

Inclusion Exclusion
• Original observational studies or reports; primarily cross-sectional and cohort studies • If more than one article presenting results from the same study existed then only the most relevant article was included.
• Studies reporting results specifically on people aged 60 and over • No reviews, experimental or clinical trials, or studies with subsample of the original study sample, unless it is still a representative sample and reports new relevant information • Representative of the general population (study samples from nursing homes, etc. are accepted) • No working populations • Only following musculoskeletal (MSK) conditions: 1)Non-specific extremity MSK 2)Back pain (+ divided by region) 3)Osteoarthritis in larger joints of the extremities (i.e. shoulder, elbow, hand/wrist, hip, knee, ankle/foot) 4) Rheumatoid arthritis 5) Osteoporosis • No native/aboriginal populations • Studies from developed countries only (e.g. countries with "advanced economies" according to IMF) • Studies reporting general MSK pain with no specific anatomical area • Any type of prevalence/incidence • No traumatic related injuries • Prevalence/incidence estimates specifically on people aged 60 and over • No secondary MSK conditions (i.e. osteoporotic fractures) • In studies with results from more than one period/survey, only the latest • No combined anatomical sites (e.g. neck + shoulder pain), except for back pain which is usually low back pain.
the title and abstract. This was followed by retrieval of all full-text articles for further eligibility. As Pubmed adds papers or change MeSH terms retrospectively, the search was repeated after July 1 st . The last search was conducted September 1 st 2011. No additional searches were conducted, nor were any authors contacted.

Eligibility criteria
Only observational studies from developed countries that reported specific MSK disorders on older people aged 60 and over were included. Thus, studies reporting general MSK pain were excluded. Preferably, the study sample had to represent the general population, but as some individuals may live in nursing homes etc., such studies were also accepted. Table 1 lists the full inclusion and exclusion criteria used in this literature review.

Extraction of information
All core information from the included studies was extracted by an unblinded examiner. The most relevant information were: Article details, study objective(s), study design, method of data collection, sampling method and sample data, disease definition, and outcome data ( Table 2). If the included study referred to another reference (i.e. another paper, report, or website) for a more detailed description of the study cohort, then that reference was perused for additional information if it was accessible.

Risk of bias assessment
The quality of each study was determined by assessing the risk of bias [8]. Recently, Viswanathan et al. have identified 29 practical and validated items that may be used to evaluate the risk of bias and precision of observational studies [9]. This bank of items covers a range of different study designs and the authors have provided instructions as to what items to use depending on the studies under assessment. Thus, only items related to our main objectives were identified and criteria for each item were defined to fit our main objective ( Table 3). The layout of the questionnaire was slightly modified for practical reasons, but no other changes were made. The chosen items focused on selection bias, information bias, and the overall interpretation of each study. Relevant criteria to assist in determining the risk of bias in a study were specified to each item. No validation of the included items was performed.

Data analysis
The extracted data was presented in separate tables for each of the included MSK conditions. In studies where the results were only presented graphically, best effort was made to determine the prevalence estimates from the graphs (without decimals). Both total and gender prevalence estimates as well as age related changes were reported when possible. In addition, the attempt was made to present pooled means of prevalence estimates on fairly homogeneous studies.

Search results
In total, 5097 articles were found through the search strategy ( Figure 1). Based on either their title or abstract, 185 were subsequently retrieved and reviewed. Of these, 100 articles were rejected, mainly because prevalence estimates on elderly aged 60 and over was not reported or could not be determined (82%) (Additional file 3).
Other reasons for exclusions were 1) the studies did not fulfil the inclusion/exclusion criteria (14%) and 2) articles reporting results that were already published in other articles (i.e. duplicate publications) (4%). Thus, in all 85 articles were included in this review.

Study characteristics
The included articles were published in 39 different journals of which 4 journals (Spine (26%), Rheumatology (18%), Annals of Rheumatic Diseases (18%), Arthritis & Rheumatism (15%)) accounted for approximately three quarters of all journals. There was an uneven distribution of publications between 2000 and 2011, but with no clear patterns across the decade. The majority of the studies were from Europe (58%) followed by Australasia (21%), North America (18%) and Middle East (4%).

Risk of bias within each study and across studies
Overall, 25% of the studies were determined as having a low risk of bias and 11% were deemed as having a high bias risk (Figure 2 and Additional file 4). Thus, in approximately 65% of the studies it was unclear if risk of bias were either low or high, mainly because it was difficult to determine if the final study sample was truly representative of the target population. The risk of bias for
• Ascertainment procedure for target sample described?
• Study sample representative of the target population described?
• ( Table 4). Seven (58%) were of low risk of bias [10,11,13,16,17,19,20] and only one study [18] was deemed as being of high risk of bias (Table 4 and Additional file 4). The prevalence estimates that were based on clearly defined criteria (typically the 1987 American College of Rheumatology (ACR) criteria [22]) ranged between 0.4% and 2.2%. The prevalence of RA was higher among women. No clear age related differences could be determined, but generally the prevalences were minimal across ages.

Hip OA
Only three studies on hip OA were found in this review [18,23,37], two studies on symptomatic hip OA [18,37] and one on combined symptomatic/radiographic hip OA [23]. The self reported hip OA were about three times higher (17-22%) than found through clinical examination (approx. 8%) and more common in women than in men [23]. Combined symptomatic/radiographic hip OA increased from 2% in the 60-64 year olds to 3% in the 75-79 year olds, but then decreased slightly in the 80+ year olds.
For the combined knee OA and reported pain, generally larger gender differences were seen (Table 5) and more variation in age trends were also noted [23,27,28,31,32]. Painful knee OA increased with age until approximately at age 80+ where a slight decrease was reported in two out of the four studies [11,18,25,30].
Regardless of hand OA definitions, women had more OA than men and overall, OA increased with age, although several studies also reported a slight decrease in the oldest age groups.
Five studies reported either symptomatic hand OA only [11,37] or radiographic hand OA only [24,26,29], all with different definitions and age ranges. Nevertheless, similar point prevalences were noted: Approximately 15% of the "younger" elderly population reported symptomatic hand OA. Radiographic hand OA ranged from approximately 56% in the "youngest" elderly men to 100% in the oldest women.
The point prevalence estimates of combined symptomatic/radiographic hand OA ranged from approximately 4% in the "youngest" elderly population to approximately 14% in the oldest people and were therefore less common than radiographic hand OA alone.
Regardless of the anatomical site, a steady increase in OP with increasing age for all types of OP definitions was seen. Generally, OP was two-three times more common in women than in men.
The one-month prevalence was the most common prevalence period reported and ranged between 27% and 49%. The lowest estimates were based on more restricted definitions, whereas the larger estimates (47-49%) had less restricted LBP definitions.
Overall, the prevalence estimates increased up to 80 years of age and then dropped slightly after that. With one exception [83], women reported LBP more often than men.

Back pain
Back pain was used in six studies [62,63,68,70,72,73] on five different prevalence estimates, all with different BP definitions and with a wide range in prevalence estimates. Thus, one-month BP prevalence ranged between 18% and 29%, and the point prevalence ranged from 27% to 58%. Interestingly, in two studies where 100 year olds were included, the point and one-month BP was roughly the same (27%-29%) [63,70]. Prevalence estimates were all higher among women, but age-related changes are inconclusive as most studies did not demonstrate any major changes across ages.

Mid back pain
Finally, MBP (i.e. thoracic or higher back pain) was reported in three studies [75,77,78]. The three-month prevalence was used in two studies, but with different MBP definitions and thus, the prevalence ranged between 2% [77] and 15% [75]. One study showed that pain in the "higher back" was four times more prevalent among women [78].

Prevalence of shoulder pain
Six studies reported five different prevalence periods on shoulder pain [73,77,78,84,86,88] and two studies also included upper arm pain using two different prevalence periods [87,89] (Table 8). Two studies (25%) were rated as having low risk of bias [73,77,78] and the rest as having an "unclear" risk of bias (Table 8 and Additional file 4).
All studies used different shoulder pain definition and/ or different prevalence periods. Nevertheless, in some of the studies with different prevalence periods, the estimates varied only slightly (3-5%) (65-74 year olds, men: 10%-13%; women: 18%-23%) [73,78,89]. In three studies where gender estimates were provided, women reported more pain than men [73,78,89]. Only one study provided different age intervals, which showed that shoulder pain increased slightly with age.

Prevalence of elbow pain
Elbow pain was reported in four studies [73,77,78,86] and elbow/forearm pain in one study [89], of which three different prevalence periods were used (Table 9). Two studies (40%) were of low risk of bias [73,77,78], and the rest being unclear (Table 9 and Additional file 4).
Different elbow pain definitions were used in each study. Nevertheless, similar estimates were reported for both point and three-month prevalences [73,78]. Thus, approximately 5% of men and 6%-8% of women reported elbow pain. Elbow pain increased with age [73,77]. Fewer men reported elbow pain compared to women [73,78].
Wrist and/or hand pain prevalence estimates varied greatly among the different studies. For example, as few as 14% of men aged 75+ [73] and as many as 26% of women aged 60-69 [87] reported hand pain. Also, 2% of men between 65-74 [89] and 22.5% of women (65+) [78] reported wrist/hand pain. Women reported more often wrist and/or hand pain than men [73,78,89]. Hand pain increased slightly with age in one study [73], but decreased in the other study [87].
All nine studies used different hip pain definitions, resulting in a wide prevalence range. For example, the three-month prevalence ranged between 5% and 30% in the elderly aged 65-74 [73,75,77]. Six studies reported gender specific prevalence estimates, all of which reported a higher prevalence in women [73,78,83,[90][91][92]. Age related changes were somewhat unclear and only showed small (2-4%) differences across age groups.
All 11 studies used different pain definitions which resulted in great variations in prevalence estimates. For example, in the 65-74 year olds, the one-year prevalence varied between 26% and 70% in men and between 36% and 71% [91,92]. Generally, there was an increase in knee pain with increasing age, ranging between 3% and 8% [27,73,92,94]. Some studies reported a slight decrease [91,93] whereas others found no change with increasing age [77,87]. Five studies included gender specific prevalences and all showed that more women than men reported knee pain [73,78,83,91,92].
In a Danish elderly population (70-120 year olds), concurrent neck and BP was found in 13% of women and 8% of men [68]. The same findings were reported in the USA, where 9% of 65+ year olds had both NP and LBP [82]. Jacobs et al. reported an almost twofold increase in concurrent joint pain among older people (70 and 77 year olds) with chronic BP (59% and 74% respectively) compared to those without chronic BP [72].
Widespread pain was reported in the study by Natvig et al., where 14-15% of Norwegian people aged 64-86 years had additional MSK pain (from either shoulders, elbows, hands/wrists, upper back, lower back, hips, knees, or ankles/feet) [100]. In Sweden, between 4% and 6% of men aged 65-74 with upper extremity pain also reported either NP, LBP, or lower extremity pain, whereas in women the reported prevalence was about three times higher (15%-17%) [89]. According to Vogt et al., 14% of 70 to 79 year old Americans reported concurrent MSK pain in at least four sites [84]. In the UK, three studies on multiple pain sites showed varying results among 65+ year olds, which may be due to different definitions [91][92][93]. According to Dawson et al., 11% of the older adults had both hip and knee pain [91]. Croft et al. reported slightly higher estimates (26%-33%) but included the whole body [93]. In the study by Peat et al., 40% had more than one painful joint in the lower extremity [92]. More widespread pain (up to 44 pain sites) was reported by 12%-16% of women and by 7%-13% of men aged 60 and over [87]. In Italy, "polyarticular peripheral joint pain" was reported in 28% in the same age group (65+) [30]. In a Dutch study, multiple MSK pain sites were present in roughly 28% of men and in 46% of women aged 65 and over [78].
Other studies report several MSK pain sites in more than half of the elderly people, which indicates overlapping MSK symptoms [59,75,86]. In a South Korean elderly population (65+), more than half reported both upper extremity pain as well as LBP and/or lower extremity pain [59]. Similarly, in an Israeli population of elderly people aged 61 and over, more than half reported LBP, NP, knee and shoulder pain [86]. Furthermore, at least a third of these people also reported other peripheral joint pain sites. Finally, in a Spanish study, people aged 65 and over had on average four MSK pain sites [75]. Unfortunately, it is not possible to determine how many of these suffered from multiple pain sites. Thus, based on these three studies, a high degree of overlapping/concurrent MSK pain sites must be present [59,75,86].

In summary
The prevalence of MSK conditions remains high even in old age regardless of the type of complaint. Women typically report problems more often than men, regardless of the MSK condition. The prevalence of MSK complaints typically drops slightly in the oldest age group (i.e. 80+ year olds), except for OP where all studies report an age related increase. Widespread/concurrent MSK pain is very common among elderly people, affecting every second or third elderly person.

Summary of evidence
In this review a great variation in prevalence of MSK disorders in older people were found. The most likely reasons for these differences are: 1) different pain definitions, 2) different prevalence periods, 3) different age intervals, and 4) the prevalence estimates were either divided by gender or only reported as a total prevalence estimate. Thus, it is impossible to determine any overall estimates on the prevalence of MSK problems in the elderly population.
Nevertheless, some general observations can be drawn from this review that needs to be discussed. Musculoskeletal disorders remain prevalent in the elderly population. Especially, OA is very common among elderly people, followed by knee pain, BP, and for women also OP. Pain mechanisms in the older population are poorly understood, but it is generally believed that pain at younger ages continues in the older ages [101]. Thus, pain in the elderly should be regarded as a continuum of pain from earlier years [101].
Women tend to report MSK pain significantly more often than men in almost all studies. This gender difference in pain reporting is well known, but the reason for this is probably multifactorial with both biological and psychosocial underlying mechanisms. These different pain mechanisms are beyond the scope of this paper to discuss in detail, but are presented in a review by Fillinghim et al. [102].
There is a general trend that prevalence estimates either remain fairly constant with increasing age or that they drop slightly in the oldest people, typically from 80 years of age and onwards. An exception from this is OP, where a steady increase is reported with increasing age.
There are several potential explanations for this decline in pain reporting with age. It may simply be a general birth cohort effect which may reflect both cultural and public health related differences between for example 40 year olds and 80 year olds [103]. This potential cohort effect may be more pronounced in crosssectional studies, which were the only included studies in this review. A parallel to this may be that pain is accepted by the elderly as part of becoming old [104]. In other words, pain becomes a natural part of their life and therefore become less disturbing or simply ignored. It is also known that pressure pain decreases with age [105]. Finally, a decline in pain prevalences in the oldest old could be explained by a "survival of the fittest" phenomenon [103]. However, MSK pain itself does not lead to premature mortality per se [106][107][108]. Furthermore, this "biological elite" phenomenon is probably slowly diminishing as health and living standards in the World is generally improving and thus, more people are living longer and generally at better health Finally, there is a considerable degree of overlapping MSK symptoms as approximately every second or third elderly have widespread MSK pain. This trend is most likely part of a continuum from widespread pain at younger ages as previously mentioned [101].

Comparisons with other reviews
To our knowledge, no previous systematic literature reviews on a broader range of MSK conditions in elderly populations exist. However, a few reviews on some of our MSK conditions in the elderly populations were identified. Woolf and Pfleger reported high prevalence estimates in the elderly people for OA, RA, OP, and LBP in the developed countries [4]. In all four MSK diseases, the same age related increase in prevalence was found in their review, except for LBP where it remained fairly constant.
A literature review on LBP before 2000 found only 12 prevalence estimates specifically on elderly populations, but the authors were unable to make any general estimates mainly because of the different (or lack of ) LBP definitions as well as the varying age intervals [109]. In a more recent LBP review published in 2006 on age related changes, concluded that "benign" LBP decreased with age, but that more severe LBP increased with age [110]. Due to the heterogeneity of these studies and the aim of their review, no attempt was made to provide any general LBP prevalence estimates.
Luime et al. published a review in 2004 on shoulder pain [111]. The point prevalence on subjects <70 ranging 7%-27% was very similar for subjects older than 70 (12-26%), but this may be due to the varying pain definitions.
Dagenais et al. found a steady increase in hip OA with increasing age, ranging from 5% (60-64 year olds) to 14% (85+ year olds), and being more prevalent in women [112].
It is impossible to compare our results with the abovementioned reviews, as they too fail to provide pooled estimates due to the high degree of heterogeneity across the included studies. Nevertheless, a general increase in prevalence with age and a gender difference were reported in all reviews, which is in accordance with our own findings.

Methodological issues
The heterogeneity of pain definitions is already a well known problem, but undoubtedly, researchers have many good reasons for why they use a specific and perhaps unique pain definition. Unfortunately, this makes it impossible to draw any general conclusions based on the currently available literature. However, it would be recommendable if authors would at least report one or two additional standardised measures, such as the questions from the standardised Nordic questionnaire on musculoskeletal pain [113]. Although, journals restrict the sizes of their papers by limiting the number of words or tables and hence, decreasing the amount of information available from the studies, it is becoming more and more common to have supplementary tables published via the publishing journal's website. Such tables could include valuable information on gender specific and total prevalence estimates for future reviews to calculate pooled prevalence estimates.
It also needs mentioning that nearly twice as many prevalence estimates could have been obtained from 82 additional studies, if only authors had reported age specific estimates. So, just like the standardisation of pain definitions is warranted, standardisation of age interval reporting would also be preferable. This way, more information on age related changes from the current literature could easily have been obtained.
In this review, we found that many authors state that their results are representative of the general population. However, only few actually document this. While many do their best at obtaining a random and representative target sample from the background population, an actual non-response analysis is rarely performed. For this reason, the risk of bias of the majority of the studies (65%) was deemed unclear. Studies were generally judged as having an "unclear" risk of bias because information was missing in the study description. In other words, the external validity of these studies is questionable, which is essential in epidemiological studies. It is therefore important to either report and/or adjust for non-response bias in future studies.

Strengths and limitations of this review
Just like our included studies, our review has also some limitations that need to be addressed. We only included one electronic database (Pubmed) and thus, may have missed some relevant articles. Based on other reviews on similar MSK conditions, who have included other electronic databases (i.e. EMBASE, CINAHL, etc.), we may have missed between zero and 12% potentially relevant articles [109][110][111][112]. However, given the large heterogeneity and therefore lack of proper summary prevalence estimates, we doubt any missed articles would have had any major impact on our results. Our search strategy was also limited to the elderly population through MeSH terms. This may have lead to exclusion of some studies if for some reason they were not properly indexed in Pubmed. As only English language articles were included, any articles published in national non-English medical journals are missing in our literature review. Finally, the selection of articles was only conducted by one author, thus, there is a risk of missing potentially relevant articles. According to Edwards et al., an average of 9% of relevant articles may be missed (ranging between 0 and 32%) [114]. Thus, on average we may have missed approximately 8 articles.
The results from the included epidemiological studies must be viewed in light of the quality of these studies which depends on both the internal validity and if the results can be extrapolated to the background population (i.e. the external validity). In this review, the risk of bias rather than the quality of the studies were used as we wished to determine if the results were "believable" and not just if the "reporting" was satisfactory. The risk of bias assessment on randomised clinical trials is also recommended by the Cochrane Collaboration [8] and recently a set of risk of bias items were developed by Viswanathan et al. [9] which allowed us to design an assessment sheet well suited for our needs. However, assessing the risk of bias demands a high degree of judgement, is more time consuming, and may result in greater variability of interpretations of the studies [9,115]. Therefore, no attempt at adjusting the prevalence estimates based on the risk of bias judgment was made. Instead, we leave it up to the readers to decide on how to utilise our risk of bias judgments.
Because MSK pain may be reported as part of a larger health related publication and because a wide set of MSK conditions were included in our review, it was necessary to have rather broad search strategy. This in turn, resulted in a very large number of hits that had to be perused to seek for any potentially relevant articles. While the search may have been fairly sensitive in catching relevant articles it cannot be considered to be very specific. This becomes clear as less than 4% of the initial search results were retrieved and only 46% of those included. We did not attempt to specify the literature search any further as some of the included articles would have been missed, especially those articles where the reporting of MSK conditions are "secondary" findings.
Another limitation is the choice of only investigating the prevalence of MSK disorders among elderly people and, hence, excluding information on burden and costof-illness of these MSK conditions. Clearly, the presence of pain does not reflect how MSK problems affect older people on a daily basis. However, in the 2003 WHO report, Woolf and Pfleger reported that MSK conditions have a major societal impact in terms of reduced work disability, which would affect the "younger" elderly people aged 60-65, and result in an increased use of health care services [4]. Finally, with increasing OP, there is a high risk of fracture incidences. As most MSK conditions remain fairly common in the elderly populations and as the number of elderly people increases in the future, the socioeconomic burden of MSK in the elderly population will also increase. Thus, there will be a further need for health care professionals to deal with chronic MSK conditions among the elderly people.

Future perspectives
This review has looked at the prevalence of a series of musculoskeletal conditions in the elderly population and will serve not only as a reference for future studies, but also as a guide for clinicians in general. Firstly, a larger population of geriatric patients must be expected in the future and thus calls for more attention on developing optimal geriatric patient management protocols. Secondly, it is important for a person to maintain a sufficient functional capacity in order to maintain an active life at older age [3]. In other words, political programmes as well as primary and secondary health care programmes accommodated to the future needs are necessary in order to maintain (or ideally improve) the quality of life in the elderly population.

Conclusions
No overall estimate on the prevalence of MSK problems in the elderly population can be determined due to the heterogeneity of the studies. However, MSK disorders are common in the elderly population and women have more often MSK problems than men. There is a general trend that prevalence estimates either remain fairly constant or increase slightly with increasing age. However, for many MSK conditions, there is a slight decrease among the oldest (80+) people. Finally, many elderly people report multiple MSK pain sites.