Obesity is a word derived from French. It is often referred to as obesity. Abnormal (hyperplasic) and excessive (hypertrophic) fat accumulation in the fat tissues to the extent that it disturbs the health. The body fat ratio occurs with body weight increasing by 15-18% in men and 20-25% in women.
Useful articles about obesity and joint health is below
Influence of obesity on the development of osteoarthritis of the hip: a systematic review
Objective. To evaluate the evidence for the influence of obesity as a risk factor for the occurrence of osteoarthritis (OA) of the hip.
Methods. A bibliographical search of Medline, EMBASE and the Cochrane library until April 2000 was carried out. Articles describing studies of the relationship between obesity and the occurrence of hip OA were selected. The quality of the studies was assessed with a standardized set of criteria. The outcome of the studies was compared with respect to study characteristics and the quality score for the study. A best‐evidence synthesis was used to summarize the results of the individual studies.
Results. Five longitudinal and seven cross‐sectional studies were included in this review. There was no association between outcome and study design or methodological quality. The associations between obesity and hip OA were, however, stronger in studies in which the diagnosis of hip OA was based not only on radiological criteria but also on clinical symptoms. Overall, moderate evidence was found for a positive association between obesity and the occurrence of hip OA, with an odds ratio of approximately 2.
Conclusion. The evidence for a positive influence of obesity on the development of hip OA is moderate.
Osteoarthritis (OA) of the hip is a major cause of morbidity and disability in the elderly. This problem increases with the current ageing of the population in western societies. In addition to the pain and discomfort it causes, OA has major economic consequences .
Studies in Europe have estimated that approximately 7–25% of Caucasian individuals over the age of 55 yr suffer from hip OA; these estimates vary due to differences in the definition of OA or the selection of the study population. The prevalence of hip OA appears to be lowest in Asians, followed by African black and Native American populations, and is highest in white Europeans [2–5]. Over the last two decades many epidemiological studies have investigated the determinants of OA. These studies are important if we are to improve our understanding of the mechanisms leading to OA and to determine whether (modifiable) risk factors exist for which preventive interventions can be developed and investigated.
A frequently studied object of interest is weight, or body mass index (BMI), and its relationship with OA. A review published in 1998 showed that people with a higher BMI are more prone to the development of knee OA. However, due to sparse data and inconsistencies in the reported studies, the impact of obesity on hip OA was less clear .
Because several new studies investigating the relationship between hip OA and obesity have been published, we decided to investigate this topic using modern methods for systematically identifying and assessing the available studies. The result may be of considerable practical and theoretical importance for the management of this disease, including preventive measures.
Identification and selection of the literature
To identify observational studies on this subject, relevant publications were searched using the following databases: Medline (1966 to April 2000), Cochrane library (1993 to April 2000) and EMBASE (1980 to April 2000). The following key words were used: [hip and (arthritis or arthrosis or osteoarthritis or osteoarthrosis) or coxarthrosis] and (risk factor or causative or determinants or predictor or aetiology) and (case–control or retrospective or prospective or longitudinal or follow up or cohort). (A detailed list of the key words used can be obtained from the corresponding author.) We optimized the search strategy by looking at the specificity and sensitivity of different strategies. We tried to be as sensitive as possible within the bounds of feasibility, because of difficulty in finding the right key words and the different types of design. The search was extended by screening the reference lists of all relevant articles identified.
A study was eligible for inclusion if it fulfilled all of the following criteria: (i) one of the aims of the study was to investigate an association between hip OA and obesity; (ii) the article was written in English, Dutch, German, French, Danish, Norwegian or Swedish; (iii) the article was a full‐text article; (iv) the patients in the studies had to suffer from radiological and/or clinical hip OA, had had a (total) hip replacement (THR) or were on the waiting list for one; and (v) the study was of a cohort, case–control or cross‐sectional design.
A study was excluded if the studied population had a specific underlying pathology, such as trauma (fractures), infection, rheumatoid arthritis, ankylosing spondylitis, Perthes' disease, tuberculosis, haemochromatosis, sickle cell disease, Cushing's disease or femoral head necrosis.
Identification of all relevant articles is crucial to the validity of a systematic review . The amount of potential publication bias in our study was analysed by means of a funnel plot, in which the study outcome was plotted against the sample size of the study. In the absence of publication bias, the plot will resemble a symmetrical inverted funnel ; because of the small number of studies included and the lack of the required data we could not perform a test for symmetry, so we visually examined the funnel plot for symmetry.
Methodological quality assessment
The methodological quality of observational studies can vary considerably, which may influence the results and conclusions of the studies at issue and consequently also the results and conclusions of a systematic review. Therefore, the quality of each included paper was assessed using the following method. Two reviewers (AML and SMABZ) independently scored the quality of the selected papers according to a standardized set of criteria (Table 1). These criteria have been used in previous reviews of observational studies in the field of musculoskeletal disorders [8–10] and were modified to cover the topic of our review. The criteria concern both the internal validity and the informativeness of the study. Only items reflecting the internal validity of the studies were used to assess the methodological quality.
In case of disagreement, both reviewers tried to achieve consensus; if the disagreement was not resolved, a third reviewer (BWK) was consulted in order to achieve a final judgement.
Several items are not applicable to certain types of study design (e.g. cohort or case–control study), and therefore do not contribute to the total score of that particular study. This means that the maximum score (100%) for each study was based only on the items applicable to that particular type of study design. Positive scores were summed to give an overall internal validity score.
aV is a criterion of validity/precision; I is a criterion of informativeness.
bCH, applicable to cohort studies; CC, applicable to case–control studies.
Best evidence synthesis
Because the observational studies were considered to be heterogeneous with regard to the population studied, methodological quality and determinants and outcome measures for hip OA, we followed standard practice and refrained from statistically pooling the data and performed a ‘best evidence’ synthesis [8, 11–14]. First, the studies were classified according to the type of study design. A prospective cohort study was judged as the preferred design, followed by a case–control study, and then by a cross‐sectional study. After that, the studies were ranked according to their methodological quality score. The following ranking of the levels of evidence was formulated [8, 10, 11]:
Strong evidence is provided by generally consistent findings in multiple high‐quality cohort studies.
Moderate evidence is provided by general consistent findings
in one high‐quality cohort study and two or more high quality case–control studies or
in three or more high‐quality case–control studies.
Limited evidence is provided by (general consistent) findings
in a single cohort study,
in one or two case–control studies or
in multiple cross‐sectional studies.
Conflicting evidence is provided by conflicting findings (i.e. <75% of the studies reported consistent findings).
No evidence is provided when no studies could be found.
A study was considered to be of high quality if the methodological quality score was ≥60%. This level was chosen at the mean of all quality scores .
Two researchers (AML and SMABZ) collected the characteristics of the included studies independently of each other. They collected items on the definition of the study population, how the presence or absence of hip OA was assessed, the assessment of obesity, if the study corrected for potential confounding factors and which results were reported.
When a study reported several outcomes because of a division of the study population into subgroups, the separate outcomes were combined (where possible) using Mantel Haenszel statistics, by methods described by Clayton and Hills  or the method described by Tan et al.  as appropriate.
Identification and selection of the literature
A total of 2921 references were identified initially; of these, only nine articles met our selection criteria [4, 18–25]. The most frequent reasons for failing to meet our criteria were that there was not an appropriate study design (case reports, no data on the control group) or no specific information about the relationship between obesity and hip OA.
After screening the reference lists of the selected studies, another four studies were included [26–29]. All of them were indexed in Medline but used other descriptions of the study design. Hartz et al. used the term ‘health survey’  and van Saase et al. used the term ‘epidemiological survey’ . The other two studies did not specify the study design [27, 29]. We tried to optimize the search strategy by deleting the type of study design as one of the required key words. This improved the sensitivity, but the specificity would then have been too low (4431 instead of 1513 hits in Medline for four more articles). For one study, there were two publications reporting different aspects of the study [22, 24]. Both publications were used to extract data regarding the methods used and the results reported. Thus, finally, 12 studies were included in this review.
To investigate the amount of publication bias for our study, a funnel plot was made (Fig. 1). The plot shows the relationship between the distribution of the point estimates of the association between obesity and hip OA, and the sample size (n). Although the plot shows a more or less equal distribution, there is a lack of small studies showing an inverse association.
Description of the studies
Table 2 gives a detailed description of the characteristics of the included studies. Only five studies had a longitudinal design, viz. one prospective cohort study  and four retrospective case–control studies [21–23, 25], whereas the remaining seven studies reported only cross‐sectional associations between obesity and the presence of OA [4, 18, 20, 26–29]. In two of the 12 studies, the studied population was hospital‐based [23, 27]. The other 10 studies were population‐based.
Three studies included only males [19, 22, 23] and two others included only females [21, 25]. The ages of the studied populations diverge, but most studies investigated subjects aged 40 yr and older. All studies were carried out in the USA [4, 19, 21, 23, 26, 27, 29] or in Northern Europe [18, 20, 22, 25, 28]. Most of the studies determined obesity with the BMI. One study used the ideal body weight  and another study used relative weight ; both measurements were derived from a normal distribution of height and weight in the population . One study used weight only .
The method of assessment of hip OA varied in several studies. Two studies relied on clinical information only [19, 20], three other studies used an X‐ray score only [4, 26, 28] and another three studies used a combination of these two [21, 23, 29] as an outcome measure. Three studies used a (total) hip replacement (THR) or waiting for a THR in a specific period as an outcome [18, 22, 25]. One study did not describe clearly how hip OA was assessed; i.e. whether it was clinical only or also used X‐ray information .