Dr S Karmali, Royal Alexandra Hospital, Room 405, Community Services Center, 10240 Kingsway, Edmonton, Alberta, Canada T5H 3V9. E-mail: email@example.com
Osteoarthritis is a common progressive disease leading to joint pain and severe disability. It is a complex multifactorial disease leading to damage of cartilage, deposition of subchondral bone matrix and release of pro-inflammatory cytokines. Obesity is an emerging epidemic and also an important risk factor for osteoarthritis. Weight loss has been shown to improve pain and function in hip and knee joints with osteoarthritis. Bariatric surgery currently is the only evidence-based approach to marked weight loss in obese individuals. However, there is currently limited literature to evaluate the role of bariatric surgery in hip and knee osteoarthritis. The objective of the present study was to systematically review the literature regarding the effectiveness of bariatric surgery in obese adult patients in improving large weight-bearing joint (hip and knee) osteoarthritis. Published English-language manuscripts were considered for review inclusion. A comprehensive search of electronic databases using broad search terms was completed. From a total of 400 articles, eight articles were identified. A total of six studies were included for qualitative analysis. A general trend was identified indicating improved hip and knee osteoarthritis following marked weight loss secondary to bariatric surgery. This systematic review demonstrates that bariatric surgery may benefit obese patients with hip or knee osteoarthritis. However, this review identifies the need for randomized controlled trials to clarify the role and indications for bariatric surgery.
Osteoarthritis is an age-related, progressive disease that leads to joint pain and severe disability. Despite it being one of the most common clinical conditions in individuals in the Western world, the aetiology is relatively unknown. Osteoarthritis is proposed to be a multifactorial disease characterized by degradation of cartilage matrix, inappropriate deposition of subchondral bone matrix and increased local pro-inflammatory cytokines. Although age is an important risk factor, obesity is considered one of the main modifiable risk factors (1–3). A population-based study by Coggon et al. reported a significantly increased odds ratio of 13.6 for developing knee osteoarthritis in individuals with body mass index (BMI) over 36 kg m−2 compared to controls (4). Furthermore, they reported an exponential increase in knee osteoarthritis with increasing weight. In a similar population-based study, the odds of developing hip osteoarthritis was reported to be 1.7 times greater in individuals with a BMI of greater than 28 kg m−2 compared to those with a BMI less than 24.5 kg m−2(5). In an Australian epidemiological study, BMI greater than 30 kg m−2 was shown to increase the risk of knee osteoarthritis 20 times (6). However, according to the Framingham Study, the association between weight and knee osteoarthritis was stronger in women than men (7). Nevertheless, obesity was initially believed to worsen osteoarthritis of the hip and knee secondary to increased mechanical loads. However, recent evidence suggests that it may also play a role in overproduction of pro-inflammatory molecules, which may subsequently damage articular tissue (8,9). Based on population-based data collected, Coggon et al. estimated that reduction of BMI to normal range may reduce the incidence of knee osteoarthritis by 57% (4). Additionally, a reduction of BMI to normal range has been estimated to reduce hip osteoarthritis by 25% (7). Weight loss secondary to lifestyle modifications has been shown to improve joint pain in obese patients (9). Messier et al. randomized 316 elderly overweight and obese adults with knee osteoarthritis and compared diet only, exercise only and diet with exercise to controls, focusing on changes in physical disability (10). They reported significant improvements in self-reported physical function and knee pain in overweight and obese individuals treated with diet plus exercise compared to controls. Similarly, Huang et al. also reported significant improvement in knee pain following weight reduction in patients with bilateral knee osteoarthritis (11).
Description of the intervention
Currently, bariatric surgery as part of an overall weight management strategy has shown to produce marked sustainable weight loss (12). Bariatric surgery is comprised of multiple surgical procedures, generally categorized as either primarily restrictive or malabsorptive. Primarily restrictive bariatric surgical procedures include laparoscopic adjustable gastric banding (LAGB) and laparoscopic sleeve gastrectomy (LSG). Primarily malabsorptive bariatric surgical procedures include roux-en-Y gastric bypass (RYGB) and biliopancreatic diversion with or without duodenal switch (BPDDS).
Why it is important to do this review
Recently, evidence has reported marked weight loss and improvement in comorbidities in obese patients following bariatric surgery (12,13). This includes comorbidities such as type 2 diabetes mellitus, hypertension and obstructive sleep apnea. Although weight loss following lifestyle modification has been reported to improve joint pain (9), there remains a paucity of research assessing whether weight loss following bariatric surgery is effective at relieving or improving joint pain in weight-bearing joints such as hip and knee joints with osteoarthritis.
To systematically review the literature regarding the effectiveness of bariatric surgery in obese adult patients in improving large weight-bearing joint (hip and knee) osteoarthritis.
Criteria for considering studies for this review
Types of studies
Randomized controlled trials, non-randomized controlled trials, case-controlled studies and case series.
Types of participants
The target population consists of adult (>18 years old) obese (BMI > 30 kg m−2) male or female patients and undergoing bariatric surgery with hip or knee joint pain, osteoarthritis.
Types of interventions
The intervention under study was bariatric surgery performed on obese individuals. This included LAGB, LSG, RYGB and BPDDS.
Types of outcome measures
Primary outcomes. The primary outcome was change or improvement in hip or knee joint pain. This included pain score by the visual analogue scale, knee society score (KSS) or Harris hip score (HSS).
1Joint space width;
2Patient overall satisfaction;
3Severity of osteoarthritis;
4Quality of life.
Search methods for identification of studies
Published English-language manuscripts were considered for review inclusion. A comprehensive search of electronic databases (e.g. MEDLINE, EMBASE, SCOPUS, BIOSIS Previews and the Cochrane Library) using broad search terms was completed.
Searching other resources
The bibliographies of all included articles were examined to identify additional potentially relevant publications. Ongoing trials were identified using controlled trial registration websites, including ICRTP Search Portal for the World Health Organization.
Data collection and analysis
Selection of studies
All studies involving bariatric surgery in obese patients with assessment of hip or knee joint pain or osteoarthritis were included. One author (X. S.) experienced in database searches conducted the electronic searches, and one author (R. G.) conducted a pre-screen to identify the articles clearly irrelevant by title, abstract or keywords of publication. Two independent reviewers (R. G. & D. A.) then assessed the studies for relevance, inclusion and methodological quality. Articles were classified as either:
1Relevant (meeting all specified inclusion criteria);
2Possibly relevant (meeting some but not all inclusion criteria);
3Rejected (not relevant to the review).
Two reviewers (R. G. & D. A.) independently reviewed full-text versions of all studies classified as relevant or possibly relevant. Disagreements were resolved by re-extraction.
Data extraction and management
Two reviewers independently extracted data from the full versions of the manuscripts. The extracted information included details of demographics (e.g. age, BMI, etc.), clinical characteristics of each group, study inclusion and exclusion criteria, details of intervention, baseline and post-intervention outcomes. Disagreements were resolved by re-extraction when necessary.
Assessment of risk of bias in included studies
All included trials were assessed independently by two reviewers for methodological quality using the Cochrane Risk of Bias tools (14). Disagreements were resolved by re-extraction when necessary.
Assessment of reporting biases
Data synthesis. Two independent reviewers completed data extraction (X. S. & R. G.); analysis was descriptive. Simple means and counts were reported. Meta-analysis or pooled analysis was deemed not appropriate due to the high heterogeneity among the included studies and variability in assessment tools used for reporting outcomes.
Results of the search
A total of 400 articles were identified using our search criteria for screening (Fig. 1). Following assessment by our exclusion criteria, 16 articles remained for abstract review. From this total eight studies were identified, of these two were excluded and six studies remained. Thus, a total of six studies assessing bariatric surgery effects on hip and knee joint pain were identified following careful screening, of these five were case series (9,15–18) and one was a case-controlled study (19).
All six included studies reported outcome data including hip or knee joint pain. The baseline patient characteristics in the included studies are listed in Table 1. The number of patients in the included studies ranged from 14 to 1,203 patients. The mean patient age ranged from 37 to 56 years. Patients undergoing bariatric surgery had a BMI ranging from 41 to 51 kg m−2, as shown in Table 1.
Table 1. Patient demographics of included studies
Number of patients (n)
Initial BMI (kg m−2)
Length of follow-up (years)
Level of evidence
Level of evidence according to the Oxford CEBM Levels of Evidence (27).
BMI, body mass index; CS, case series; LAGB, laparoscopic adjustable gastric banding; RYGB, roux-en-Y gastric bypass.
The primary outcome of hip and knee joint pain was assessed by all six included studies as shown in Table 2. However, the included studies varied in the assessment tools used to evaluate the patient's hip or knee joint pain. Three of the included studies reported both hip and knee joint pain (15,17,19), while three reported only knee pain (9,16,18). Parvizi et al. and Abu-Abeid et al. reported knee pain using the KSS (15,16). The KSS is a scoring system that combines an objective knee score that is based on clinical parameters with a functional score based on how the patients perceives the knee's function. The maximum score is 100 for the knee score and 100 for the functional score, therefore an overall maximum of 200 points, which indicates a normal knee joint. The HSS is a similar tool in which scoring is based on questions regarding hip pain, function, functional activities (i.e. how you climb stairs?) and physical exam. The highest score is 100 points, which indicates a highly functional, pain-free hip joint. Richette et al. used a visual analogue scale to assess knee pain before and after bariatric surgery in obese patients (9).
Table 2. Osteoarthritis outcomes following bariatric surgery in included studies
A systematic review of the existing literature demonstrates a paucity of evidence assessing the effectiveness of bariatric surgery and subsequent weight loss on hip and knee joint pain associated with osteoarthritis. Furthermore, there is a considerable amount of variability among the included studies regarding the assessment tools used to evaluate hip or knee joint pain and osteoarthritis. However, the available evidence seems to support the effectiveness of bariatric surgery and subsequent weight loss in improving hip and knee pain associated with osteoarthritis.
Despite osteoarthritis being a very common problem in weight-bearing joints, especially in the aging population, obesity has been identified as the main modifiable risk factor (1–3). Obesity translates into increased mechanical forces on hip and knee joints, leading to disability in an aging population. In the USA alone, 34 million adults are classified as obese. In Canada, approximately 60% of the population is considered overweight with approximately 24.1% of the adults defined as obese (20,21). However, obesity has also been proposed to accelerate damage to joints through increased systemic inflammation (9). This is supported by Peltonen et al.'s observations that the prevalence of hip and knee pain leading to work restriction is greater in obese individuals compared to the general population (19). The increased adipose tissue in obese individuals is hypothesized to act as an endocrine organ, generating and releasing pro-inflammatory mediators, which may lead to damage of cartilage within joints (22–24). Fogarty et al. reported a linear association between increased level of C-reactive protein and an increase in weight in 1,222 patients over a 9-year period (25). Furthermore, Richette et al. report significantly improved levels in N-terminal propeptide of type IIA collagen levels (marker of cartilage synthesis) and decreased levels of cartilage oligomeric matrix protein (marker of cartilage destruction) following substantial weight loss subsequent to bariatric surgery (9).
This systematic review demonstrates improved hip and knee joint pain associated with osteoarthritis following bariatric surgery and subsequent weight loss. These findings are supported by a recent meta-analysis of four randomized controlled trials, which reported on weight reduction and knee osteoarthritis (26). Christensen et al. reported significantly improved disability in the knee joint following a weight reduction over 5.1%. Interestingly, weight change alone could not predict change in the knee pain score. Messier et al. reported improved function and pain by older obese patients following modest weight loss and moderate exercise (10). However, bariatric surgery has been shown to produce markedly greater weight loss in obese individuals. Abu-Abeid et al. reported a BMI change from 43.3 to 37 kg m−2 following LAGB, which resulted in both improved pain and function scores according to the KSS (16). Furthermore, they reported increased joint space width within the knee joint following the weight loss. Hooper et al. reported decreased frequency of MSK symptoms in the knee following a BMI decrease from 51 to 36 kg m−2 post bariatric surgery (17). Interestingly, a significant improvement in MSK symptoms in the hip joint was not seen in these patients.
A weakness of the current systematic review is the inability to perform a meta-analysis or a pooled analysis. The quality of a systematic review is based on the quality of the primary studies. Unfortunately, no randomized controlled trials have been conducted assessing the impact of bariatric surgery and subsequent weight loss on hip and knee osteoarthritis. There is apparent variability in outcome reported among the included studies, which may be related to the challenges in reporting hip and knee osteoarthritis outcomes. Unlike other obesity-related comorbidities such as type 2 diabetes mellitus, there are less objective measures to quantify severity of disease. Subjective pain and functional questionnaires and scoring systems are currently utilized, however are not standardized. However, despite the strong evidence supporting bariatric surgery and weight loss in obese patients and the concurrent evidence suggesting weight loss may improve hip and knee osteoarthritis, limited research has been conducted to assess both. This systematic review highlights the calls for further high-quality randomized studies to be performed with appropriate control subjects. Furthermore, standardization of outcome reporting for hip and knee osteoarthritis may lead to improved integration of studies.
In conclusion, bariatric surgery as part of a comprehensive weight management strategy with subsequent marked weight loss may lead to improved hip and knee pain and function in obese patients with osteoarthritis. However, further research is needed to clarify the underlying mechanisms and define the role of bariatric surgery in this patient population.
Conflict of Interest Statement
The authors have no conflicts of interests to disclose.