What proportion of patients report long-term pain after total hip or knee replacement for osteoarthritis? A systematic review of prospective studies in unselected patients
===========================================================================================================================================================================

* Andrew David Beswick
* Vikki Wylde
* Rachael Gooberman-Hill
* Ashley Blom
* Paul Dieppe

## Abstract

**Background** Total hip or knee replacement is highly successful when judged by prosthesis-related outcomes. However, some people experience long-term pain.

**Objectives** To review published studies in representative populations with total hip or knee replacement for the treatment of osteoarthritis reporting proportions of people by pain intensity.

**Data sources** MEDLINE and EMBASE databases searched to January 2011 with no language restrictions. Citations of key articles in ISI Web of Science and reference lists were checked.

**Study eligibility criteria, participants and interventions** Prospective studies of consecutive, unselected osteoarthritis patients representative of the primary total hip or knee replacement population, with intensities of patient-centred pain measured after 3 months to 5-year follow-up.

**Study appraisal and synthesis methods** Two authors screened titles and abstracts. Data extracted by one author were checked independently against original articles by a second. For each study, the authors summarised the proportions of people with different severities of pain in the operated joint.

**Results** Searches identified 1308 articles of which 115 reported patient-centred pain outcomes. Fourteen articles describing 17 cohorts (6 with hip and 11 with knee replacement) presented appropriate data on pain intensity. The proportion of people with an unfavourable long-term pain outcome in studies ranged from about 7% to 23% after hip and 10% to 34% after knee replacement. In the best quality studies, an unfavourable pain outcome was reported in 9% or more of patients after hip and about 20% of patients after knee replacement.

**Limitations** Other studies reported mean values of pain outcomes. These and routine clinical studies are potential sources of relevant data.

**Conclusions and implications of key findings** After hip and knee replacement, a significant proportion of people have painful joints. There is an urgent need to improve general awareness of this possibility and to address determinants of good and bad outcomes.

### Article summary

#### Article focus

*   Total hip and knee replacement have good clinical outcomes.

*   There is a perception that some people experience long-term pain after their joint replacement.

*   We aim to establish the proportion of patients experiencing long-term pain after joint replacement.

#### Key messages

*   Well-conducted studies in representative populations of patients with total hip and knee joint replacement suggest that a significant proportion of people continue to have painful joints after surgery.

*   The proportion of people with an unfavourable long-term pain outcome in studies ranged from about 7% to 23% after hip and 10% to 34% after knee replacement. In the best quality studies, an unfavourable pain outcome was reported in 9% or more of patients after total hip and about 20% of patients after total knee replacement.

*   There is an urgent need to improve general awareness that some patients experience long-term pain after joint replacement and to address the determinants of good and bad outcomes.

#### Strengths and limitations of this study

*   Systematic review conducted according to established methods and guidelines identified 17 studies in representative populations of patients with total hip or knee replacement.

*   Pain outcome data are widely recorded as mean values but only a minority of studies reported outcomes as proportions with pain at follow-up.

*   The small number of studies and different pain outcome measures precluded meta-analysis, calculation of a summary estimate and exploration of sources of heterogeneity.

## Introduction

Symptoms of osteoarthritis are managed in the community, but if pharmacological and conservative treatments provide inadequate relief, then total joint replacement is commonly performed. In England and Wales during the year ending March 2010, there were 71 021 primary total hip and 79 263 primary total knee replacement operations recorded in the National Joint Registry.1 In the USA in 2006, the estimated numbers of hospital discharges after total hip or knee replacement procedures were 231 000 and 542 000, respectively,2 with demand predicted to increase substantially.3

Total hip or knee replacement is highly successful when judged by prosthesis-related outcomes, such as the radiographic appearance of the prosthesis,4 implant survival5 or surgeon-assessed outcome.6 Nevertheless, many people continue to experience significant pain and functional problems after total joint replacement. Woolhead and colleagues7 conducted in-depth interviews with 10 patients 6-months after their total knee replacement. Although patients considered their joint replacement successful, eight of the 10 patients still experienced pain and immobility. In a European collaborative study of 1327 patients with total hip replacement, Judge and colleagues8 applied three recognised criteria for general symptomatic improvement with symptom severity based on pain, stiffness and physical function according to the WOMAC osteoarthritis index.9 The different criteria suggested that between 14% and 36% of patients did not improve or were worse 12 months after surgery.

Pain is the most important factor in the decision to recommend total joint replacement.10 Furthermore, patient-reported pain is now widely assessed using disease-specific outcome measures. In the USA, the importance of patient-reported outcomes in assessing quality of care is recognised,11 and in England, following the report of Lord Darzi,12 information is routinely collected after elective surgery.13

Reporting of pain outcomes in the orthopaedic literature frequently emphasises improvement in mean scores. An example of this is the study of Bachmeier and colleagues14 where the improvement of mean WOMAC pain scores at 3, 6, 9 and 12 months after hip or knee replacement is clearly demonstrated. However, at all time points, the mean pain score has an associated SD implying that a proportion of patients still reported pain. To advise both patients and their healthcare professionals, it is important to have a clear understanding of the frequency and extent of pain following total hip or knee replacement.

We have used systematic review methods to identify studies reporting the proportion of people with significant long-term pain after total hip or knee replacement. We aimed to identify studies in populations representative of contemporary clinical practice. Some information on all patients in cohorts is required as patients lost to follow-up may have experienced poorer or at least similar outcomes to those followed up.15–18

## Methods

We used systematic review methods in accordance with the MOOSE proposal for reporting systematic reviews and meta-analyses of observational studies.19 A MOOSE checklist is shown in online appendix 1.

### Data sources and searches

MEDLINE and EMBASE databases were searched from inception to 31 January 2011. A general search was performed to identify quantitative research in primary total hip or knee replacement. The MEDLINE search strategy is shown in online appendix 2. Search terms related to hip or knee replacement and studies with an epidemiological design including prospective and longitudinal studies. No language restrictions were applied.

Within titles, abstracts and keywords of articles identified, we searched for text words relating to osteoarthritis and *disease-specific patient-centred pain outcome measures* used in osteoarthritis and joint replacement. Specifically these were Western Ontario and McMaster Universities Arthritis Index (WOMAC), Arthritis Impact (AIMS), Lequesne, Oxford hip or Oxford knee score, Hip Osteoarthritis Outcome Score (HOOS) or Knee Osteoarthritis Outcome Score (KOOS), pain visual analogue scales (VAS) and self-appraisal. Outcomes not considered patient centred were Harris Hip, American Knee Society and Bristol Knee Scores. We did not include generic health measures including the Health Assessment Questionnaire, EuroQol, London Handicap Scale, Medical Outcomes Study Short Form-36 (SF-36), Disease Repercussion Profile, Sickness Impact Profile and WHOQol-BREF.

We also checked citations of key articles in ISI Web of Science and reference lists. Studies reported only as abstracts were excluded. References were managed in an Endnote X3 database.

### Study selection

We included prospective studies of consecutive unselected patients representative of the primary total hip or knee replacement population. Studies reporting a specific implant or component were eligible if the population studied was not clearly selected, that is, the group was likely to be representative of the total joint replacement population.

Study designs excluded were cross-sectional and retrospective studies, randomised controlled trials and evaluations of specific technologies. Randomised controlled trials and many evaluations of new technologies comprise selected populations, and furthermore, it is outside the scope of this review to assess whether these reflect best clinical practice.

We made an a priori decision to limit follow-up to between 3 months and 5 years. In evaluating the effectiveness of primary total hip or knee replacement in reducing pain from osteoarthritis, we are concerned with outcomes when recovery can be considered maximal14 and not later issues of joint loosening and revision.20

Study titles, abstracts and, where necessary, full articles were checked independently for eligibility by two researchers experienced in systematic reviews (ADB) and rheumatology (PD). Disagreements were resolved by discussion. Validity of the database was confirmed by checking against reference lists provided by local experienced researchers in orthopaedic outcomes.

While we recognise that studies may include patients with other joint replacement surgery, we excluded studies specifically describing outcomes of revision operations and partial joint replacements (eg, unicompartmental or patellofemoral knee replacement and hip resurfacing).

### Data extraction

The pain measure relating to the operated hip or knee was considered in the review. No attempt was made to contact authors of studies who did not have appropriate data. In the previous reviews we have conducted only a minority of authors contacted have provided additional data for analyses. Although contact with authors is a well-recognised approach in systematic reviews,21 a survey of review authors indicated that many systematic reviewers do not do so because of poor response rates and variability in the quality of information collected this way.22 Authors of studies with appropriate data but with specific missing information were contacted.

Data from eligible articles were recorded on an Excel spreadsheet by one reviewer (ADB) and checked against original articles by a second (VW). Data were extracted on indication (all or majority of patients with osteoarthritis), pain outcome, baseline dates, country, study design, how group selected, age, number of patients recruited, number who died and the number lost to follow-up. We recorded the number of people at follow-up with no pain or mild pain, moderate or severe pain (or with little improvement in pain from preoperative), revision or dislocations or deep infection and contralateral or other joint replacement or treatment for fracture.

### Data synthesis and analysis

As studies reported different pain measures, we summarised pain outcomes in a way that was applicable to all measures. The proportions of people with different severities of pain were summarised as ‘favourable’, ‘unfavourable’ or ‘uncertain’ outcomes. Favourable outcome includes people with no pain or mild pain at follow-up, while unfavourable outcome includes those with moderate-to-severe pain or for whom surgery had not relieved pain. The uncertain outcome includes all patients for whom we cannot be sure of their pain levels at follow-up. These include patients who died, had revision surgery, contralateral surgery or dislocation and were not followed up with questionnaires and those lost to follow-up. We also included as uncertain those patients with a degree of reported pain, which we could not classify as a favourable or unfavourable outcome.

### Quality assessment

Only studies with unselected patients and complete reporting of losses to follow-up were included. To describe the quality of studies, we used the features of the Cochrane risk of bias table applicable to longitudinal studies.21 Specifically, these were blind outcome assessment (self-completed patient-reported outcome measure), incompleteness of outcome data collection (losses to follow-up low <10%, moderate 10%–20% or high >20%) and other sources of bias (representativeness of study population).

## Results

The review process is summarised in figure 1. Searches identified 1308 studies reporting patient-centred outcomes in patients with osteoarthritis. Of these, 115 studies included data on patient-centred pain outcomes in representative population samples studied prospectively for between 3 months and 5 years. Fourteen articles describing 17 cohorts (6 in hip and 11 in knee patients) presented results classifiable as proportions of people with different extents of pain at follow-up. The main reasons for exclusion at this stage were lack of a pain outcome separate from an overall outcome score or the presentation of results as means only.

![Figure 1](http://bmjopen.bmj.com/https://bmjopen.bmj.com/content/bmjopen/2/1/e000435/F1.medium.gif)

[Figure 1](http://bmjopen.bmj.com/content/2/1/e000435/F1)

Figure 1 
Systematic review flow diagram.

Patient and study characteristics and outcomes are shown in table 1. The proportions of people with different pain outcomes are summarised in figure 2.

View this table:
[Table 1](http://bmjopen.bmj.com/content/2/1/e000435/T1)

Table 1 
Studies of total hip or knee replacement reporting proportion of patients with pain at follow-up

![Figure 2](http://bmjopen.bmj.com/https://bmjopen.bmj.com/content/bmjopen/2/1/e000435/F2.medium.gif)

[Figure 2](http://bmjopen.bmj.com/content/2/1/e000435/F2)

Figure 2 
Studies of hip or knee replacement reporting proportion of patients with pain at follow-up. Preceding study author: H (hip), K (knee) and months (follow-up). Studies ordered within hip and knee replacement groups by decreasing representativeness (multiple compared with single centre) and by increasing losses to follow-up.

### Total hip replacement

Systematic searches identified six studies from Canada, Denmark, Spain, Sweden, UK and USA including a total of 13 031 patients. Pain outcome measures were based on the WOMAC pain scale or authors' own methods. The measures used and the definition of unfavourable pain outcome are summarised for each study in online appendix 3.

### Study quality

Issues relating to study quality are summarised in online appendix 4.

Studies described data collected prospectively in consecutive patients with primary total hip replacement. One study was in patients recruited from a national joint registry.23 Two studies were in multiple centres24 25 and three were studies in single centres.26–28 Cohorts were generally similar with regard to patient age (range of means or medians 65.0–73.0 years) and sex (range of percentage female 48.3%–63%), and the indication was osteoarthritis in 87% of patients or more when specified. One national registry study from Denmark included only patients treated with a postero-lateral surgical approach.23 However, the posterior or lateral approach was used in 99% of patients according to another publication from the Danish Hip Registry.37 Otherwise, no inclusion or exclusion criteria suggested that the patients' studies would not have been representative of the overall total hip replacement population. All studies used self-completed patient reported outcome measures. Losses to follow-up ranged from 5.8% to 47.6%. We considered two markers of better representativeness as indicators of study quality: studies with multiple compared with single centres and by lower losses to follow-up.

### WOMAC pain

Jones and colleagues24 followed up a cohort of 242 consecutive patients receiving total hip replacement in a health region 6 months after total hip replacement. Patients undergoing hemiarthroplasty, revisions and emergency surgery were excluded. Losses to follow-up were low at under 5.8%. Results were presented combined with a total knee replacement cohort, and with the consent of the author, we assumed that equal proportions of hip and knee patients were followed up. The WOMAC outcome used to define a poor pain outcome was an improvement of <10 points on the 100-point pain scale (representing a gain of at least 60% of the baseline SD). We estimate the proportion of patients with no detectable clinical improvement was 8.3% (uncertain 5.8%).

Quintana and colleagues25 followed up a cohort of 784 patients on waiting lists for total hip replacement at seven teaching hospitals. WOMAC questionnaires were completed 6 months after surgery by 584 patients. Losses to follow-up were high at 25.5%. The authors identified 24.55 points on the 100-point WOMAC pain scale as representing a minimal clinically important difference. No improvement in pain greater than the minimal clinically important difference was observed in 16.3% of patients (uncertain 25.5%). The other two studies reporting WOMAC pain outcomes after total hip replacement were conducted in single centres.

Several reports described the cohort of Nilsdotter and colleagues. The prospective study with 219 consecutive patients with primary unilateral total hip replacement represented the most complete report.26 Losses to follow-up were low at about 5.9%. Of the 219 patients, only those recruited in the later stages of the study had baseline pain assessed with the WOMAC questionnaire. Thus the detectable clinical improvement outcome of 10 points on the 100-point scale was available on 92 patients. The authors reported that there were no differences between age and sex between these 92 patients and those without WOMAC data. We estimated overall numbers of patients with favourable and unfavourable outcomes on the basis of these 92 patients. Approximately 20.5% of patients had no detectable clinical improvement after a mean of 43 months (uncertain 9.6%).

In the study of Wylde and colleagues,28 1401 consecutive patients with total hip replacement were followed prospectively for a median of 41 months. In a postal survey losses to follow-up were high at 47.6%. Moderate or severe persistent pain, indicated by a WOMAC score of 0–75 points on the 100-point scale, lasting 3 months or more, was reported by 8.1% of patients (uncertain 52.7%).

### Authors own pain measure

In the study of Nikolajson and colleagues,23 1231 patients with primary total hip replacement recorded in a national joint registry were followed up by postal questionnaire at 12–18 months. Losses to follow-up were low at 5.9%. Pain from the operated hip (validated by pain drawings) with moderate to very severe impact on daily life was reported by 10.3% of patients (uncertain 28.4%).

Singh and Lewallen27 followed up a single centre population with a postal questionnaire. Of 9154 patients with total hip replacement, 5707 provided information at 24 months with high loss to follow-up of 37.7%. Moderate or severe pain in the operated hip was reported by 4.8% of patients (uncertain 37.7%).

### Total knee replacement

Searches identified eleven studies conducted in Canada, Finland, Spain, Sweden, UK and USA reporting appropriate pain outcomes after total knee replacement. Studies included a total of 12 800 patients. Pain outcome measures were based on the WOMAC and KOOS pain scales, the Oxford knee score pain dimension or VAS pain scales. The measures used and the definition of unfavourable pain outcome are summarised for each study in online appendix 3.

### Study quality

Issues relating to study quality are summarised in online appendix 4.

Studies described data collected prospectively in patients with primary total knee replacement. One study was in patients recruited from a national joint registry.29 Two studies were in patients from multiple centres,24 25 six studies were in patients treated at a single centre,30–35 and one study reported all patients operated on by one surgeon.36 Cohorts were generally similar with regard to patient age (range of means or medians 66–76 years) and sex (range of percentage female 54–86%), and the indication was osteoarthritis in 94% of patients or more when specified. In one study patients were identified before surgery but no other further details of recruitment centre were reported.31 Although one study limited inclusion of patients to those aged 50 years and older31 and another followed up patients operated on by experienced surgeons only, study inclusion and exclusion criteria suggested that all studies were likely to be representative of the general total knee replacement population. With the exception of one study which used exclusively telephone interview, all studies assessed pain at follow-up using self-completed questionnaires. All assessed pain using patient reported outcome measures. Losses to follow-up ranged from 0% to 43.5%.

### WOMAC pain

In addition to their study in hip replacement patients, Jones and colleagues24 followed up a cohort of 292 consecutive patients 6 months after total knee replacement. Patients receiving hemiarthroplasty, revisions and emergency surgery were excluded. Losses to follow-up were low at 5.8%. As previously described, assuming equal proportions followed up we estimate that a detectable clinical improvement of <10/100 points on the WOMAC pain scale (representing a gain of at least 60% of the baseline SD) was reported by 18.5% (uncertain 5.5%).

Quintana and colleagues25 followed up 792 consecutive patients from seven hospitals who received total knee replacement. At 6-month follow-up, WOMAC questionnaires were completed by 601 patients. Losses to follow-up were high at 24.1%. No improvement in pain greater than the minimal clinically important difference (22.6/100) was observed in 25.1% of patients (uncertain 24.1%).

Núñez and colleagues30 followed up a group of 88 consecutive primary total knee replacement patients. Only 5.0% of patients were lost to follow-up. At 36 months, 8.0% of patients (uncertain 23.9%) had no improvement in WOMAC pain scores.

After total knee replacement surgery, a cohort of 68 patients was followed up prospectively by Stephens and colleagues.31 Losses to follow-up were low at 7.4%. At 6 months, 16.2% of patients (uncertain 7.4%) had no change or increased WOMAC pain compared with before surgery.

Czurda and colleagues35 followed up 411 consecutive patients after computer-assisted or conventional primary knee replacement at a mean of 26 months. Painful knees, defined as moderate pain or worse in any of the WOMAC pain questions, were reported by 13.9% of patients (uncertain 19.7%). Losses to follow-up were moderate at 13.4%.

A cohort of 1394 consecutive total knee replacement patients were followed up prospectively by Wylde and colleagues28 for a median of 41 months. In a postal survey, moderate or severe persistent pain, indicated by a WOMAC pain score of 0–75 points on the 100-point scale, lasting 3 months or more was reported by 14.3% of patients (uncertain 54.7%). However, losses to follow-up were high at 45.3%.

### KOOS pain

From a postal survey of patients waiting for primary total knee replacement, Nilsdotter and colleagues33 followed 102 patients prospectively. Losses to follow-up were moderate at 12.7%. At 60 months, 26.5% of patients (uncertain 27.5%) experienced similar or more pain than before surgery.

### Oxford knee score pain dimension

Baker and colleagues29 followed up 9417 patients with primary total knee replacement from a joint registry by postal questionnaire at least 12 months after surgery. Losses to follow-up were moderate at 14.9%. Persistent knee pain was reported by 16.8% of patients (uncertain 14.9%).

### VAS pain

Lundblad and colleagues32 followed up 69 total knee replacement patients for 18 months. Losses to follow-up were moderate at 10.1%. Interpreting VAS responses, the authors reported pain at rest and on movement in 21.7% of patients (uncertain 47.8%).

Vuorenmaa and colleagues34 followed up 51 total knee replacement patients prospectively at 3 months. Losses to follow-up were moderate at 11.8%. Moderate or severe pain, defined as >30 on a 100-mm VAS pain scale, was reported in 17.6% of patients (uncertain 15.7%).

In the study of Brander and colleagues,36 116 consecutive patients treated with primary total knee replacement by a single surgeon were followed prospectively for up to 12 months. Using a VAS scale, the authors identified significant knee pain (defined as a VAS score of >40) in 12.9% of patients (uncertain 2.6%). No patients were lost to follow-up.

## Overview

### Total hip replacement

Overall, an unfavourable pain outcome was seen in at least 4.8% and up to 20.5% of patients after hip replacement (figure 2). However, these are likely to be underestimates as we do not have information on the outcomes in between 5.8% and 52.7% of patients.

As indicators of studies with more representative populations, the three studies in multiple centres reported an unfavourable pain outcome relating to the operated hip in 8.3%, 10.3% and 16.3% of patients followed up. Studies with low losses to follow-up reported an unfavourable pain outcome in 8.3%, 10.3% and 20.5% of patients. Even considering studies with some degree of outcome consistency involving minimal clinically important differences, the range of unfavourable pain outcome was wide with at least 8.1% and up to 20.5% of patients affected.

Applying the conservative assumption that an equal proportion of patients with missing data had an unfavourable pain outcome, we estimate that at least 7%–23% of patients experienced long-term pain after hip replacement. In three higher quality studies as judged by representativeness, this would reflect an unfavourable pain outcome in 9%, 13% and 20% of patients, and in three studies with low losses to follow-up in 9%, 13% and 23% of patients. Two studies with both indicators of best study quality suggested that 9%–13% of patients had an unfavourable pain outcome after total hip replacement.

### Total knee replacement

After knee replacement, an unfavourable pain outcome was seen in at least 8.0% and up to 26.5% of patients (figure 2). Three studies followed up populations from multiple centres and unfavourable pain outcomes relating to the operated knee were reported in 16.8%, 18.5% and 25.1% of patients. In four studies with low losses to follow-up, an unfavourable pain outcome was reported in 8.0%, 12.9%, 16.2% and 18.5% of patients. Considering studies with some degree of outcome consistency, the range of unfavourable pain outcome was wide with at least 14.3% and up to 25.1% of patients affected.

These are likely to be underestimates as we do not have outcome information on between 2.6% and 54.7% of patients. Assuming conservatively that the patients with missing data had similar pain outcomes, studies suggested that at least 10%–34% of patients experience long-term pain after knee replacement. Applying this assumption in the higher quality studies with potentially more representative populations, at least 19%, 20% and 31% of patients had an unfavourable pain outcome after total knee replacement. In four studies with low losses to follow-up, 10%, 13%, 17% and 20% of patients reported an unfavourable pain outcome at follow-up. In one study conducted in multiple centres with low losses to follow-up, 20% of patients reported an unfavourable pain outcome at follow-up.

## Discussion

These data show that many people with a total hip or knee replacement complain of pain in the operated joint in the early years after surgery. This was particularly evident after total knee replacement.

Although we have interpreted pain outcomes as favourable, unfavourable or uncertain, we do not believe that the data justify combination to provide summary values. In the studies identified in our review, several different outcome measures were reported, and in studies with similar outcomes, different methods of analysis were used. Without specific information on responsiveness and correlation between methods, an important additional source of heterogeneity may be introduced.38

Previous reviews have looked at functional and health-related quality of life after joint replacement. Kane and colleagues39 reported functional outcomes after total knee replacement in a literature review of 62 studies published between 1995 and 2003. They concluded that knee replacement leads to improved function as shown by large effect sizes in studies but that larger benefits were perceived by physicians than experienced by patients. Ethgen and colleagues40 identified 74 prospective cohort studies published between 1980 and 2003 that included quality of life outcomes. The authors highlighted the value of health-related quality of life data in improving management of patients undergoing hip or knee replacement. They concluded that total hip and knee arthroplasties were ‘quite effective’ in improving health-related quality of life dimensions. In a large European cohort, Judge and colleagues8 concluded that 14%–36% of patients had no symptomatic improvement 12 months after total hip replacement.

The results we present are consistent with those reporting satisfaction as an outcome. For example, Bourne and colleagues41 reported satisfaction with pain relief in a study in knee replacement patients. Satisfaction with pain relief ranged from 72% for going up or downstairs to 85% for walking on a flat surface.

In systematic reviews, publication bias is important in assessing the validity of the results. In this review, we identified 95 studies where the proportion of people with pain at follow-up could have been estimated by authors with access to original data. In previous reviews that we have conducted, replies to requests for additional data have been patchy and we chose not to pursue this approach. Nevertheless, we encourage study authors to perform and publish appropriate analyses of their data. Similarly, a wealth of patient-centred outcome data is now collected routinely and merits wide dissemination.

The majority of studies included in our review reported outcomes of patients after total joint replacement. A few studies followed up patients listed for total joint replacement, and it is possible that these studies included patients who subsequently received other surgical treatments including unicompartmental knee replacement or hip resurfacing.

In this review, we were unable to apply a standard definition of pain severity at follow-up and the need to improve assessment and measurement of musculoskeletal pain in the clinical setting is recognised.42 In the articles we included there were several interpretations of pain as an unfavourable outcome. These included lack of improvement in postoperative pain scores, pain at rest, persistent pain, night pain and lack of detectable clinical improvement.

Although having a standard outcome has advantages, our more encompassing approach allows us to include studies from wide time periods and different countries with different favoured methods for outcome assessment. However, the different outcome measures and small number of studies precluded exploration of sources of heterogeneity relating to patient characteristics, surgical method, peri-operative care and rehabilitation.

In the studies included in this review, the measures may not fully describe chronic postsurgical pain. Measures that focus on pain during specific activities may not reflect the intermittent and intense pain that has the greatest impact on quality of life.43 Another issue in considering pain as an outcome after replacement is that no account is made for the effect of analgesics and assistive aids on the reporting of pain. Self-reported analgesic use is high with 40% of men and 58% of women taking pain medications after knee replacement44 and 30% of patients taking analgesics daily after hip replacement because of pain in their replaced joint.23 We used disease-specific instruments focusing on the operated joint rather than generic measures of pain. In the replacement population, there are likely to be high levels of morbidity due to osteoarthritis and other conditions common in old age.

Our data suggest that many hip and knee replacement patients are likely to be in pain at the time when recovery from surgery should be optimal. In a cohort of 194 patients following hip or knee replacement surgery, pain was seen to achieve its lowest level by 3 months after surgery.14

While acknowledging probable underestimates of the extent of pain after surgery reported in the literature, we should recognise the effectiveness of replacement for many. However, a significant proportion of people have painful joints despite surgery and strategies to improve outcomes merit research.

Many determinants of long-term outcome after hip and knee replacement are described and interventions evaluated. Better general health, physical, emotional and social function, motivation and self-efficacy and lower levels of pain before surgery and during the rehabilitation period are associated with improved short- and medium-term outcomes.26 45–47 However, the evidence for benefit of presurgical and rehabilitation interventions is limited, particularly as few studies have been adequately powered or of sufficient duration.48–52

Another approach is the identification of patients before surgery who are at risk of a poor pain outcome. Kalkman and colleagues53 developed a multivariable model to predict short-term pain after surgical procedures. Use of a predictive model based on presurgical or postsurgical factors might allow targeting of additional pain management and rehabilitation to patients likely to benefit.

In conclusion, persistent pain in a hip or knee joint that has been replaced is not uncommon. For patients to participate in decisions about their care, it is important that they are informed and aware of both the likely benefits of surgery and the possibility of a less favourable outcome. With this knowledge, they may contribute more fully to the replacement process including preparatory strategies and long-term rehabilitation. It is clear that the current move to a greater interest in patient-centred outcomes after replacement is necessary and that there is an urgent need to address the determinants of good and bad outcomes.

## Footnotes

*   **To cite:** Beswick AD, Wylde V, Gooberman-Hill R, *et al*. What proportion of patients report long-term pain after total hip or knee replacement for osteoarthritis? A systematic review of prospective studies in unselected patients. *BMJ Open* 2012;**2**:e000435. doi:[10.1136/bmjopen-2011-000435](http://dx.doi.org/10.1136/bmjopen-2011-000435)

*   Contributors PD conceived the review. All authors contributed to the design of the review. ADB identified and acquired reports of studies. ADB and PD checked studies for eligibility. ADB and VW extracted and checked data. ADB analysed and interpreted the data. ADB drafted the manuscript. All authors contributed to the final version of the manuscript. All authors contributed to revision of the manuscript. All authors approved the final version of the manuscript.

*   Funding This article outlines independent research commissioned by the National Institute for Health Research (NIHR) under its Programme Grants for Applied Research funding scheme (RP-PG-0407-10070). The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.

*   Competing interests No financial support or other benefits have been received by any of the authors that could create a potential conflict of interest with regard to the work.

*   Patient consent We only used grouped patient data reported in published studies.

*   Provenance and peer review Not commissioned; externally peer reviewed.

*   Data sharing statement Data extracted from articles included in the review are available from author ADB.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: [http://creativecommons.org/licenses/by-nc/2.0/](http://creativecommons.org/licenses/by-nc/2.0/) and [http://creativecommons.org/licenses/by-nc/2.0/legalcode](http://creativecommons.org/licenses/by-nc/2.0/legalcode).

## References

1.  National Joint Registry for England and Wales. 7th Annual Report. Hemel Hempstead: NJR Centre, 2010.
    
    

2.  DeFrances CJ, Lucas CA, Buie VC, et al. 2006 National Hospital Discharge Survey. National health statistics reports; no 5. Hyattsville MD: National Center for Health Statistics, 2008.
    
    

3.  Kurtz S, Ong K, Lau E, et al. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am 2007;89:780–5.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.2106/JBJS.F.00222&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=17403800&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

4.  Ranawat CS, Atkinson RE, Salvati EA, et al. Conventional total hip arthroplasty for degenerative joint disease in patients between the ages of forty and sixty years. J Bone Joint Surg Am 1984;66:745–52.
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=6725322&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

5.  Aamodt A, Nordsletten L, Havelin LI, et al. Documentation of hip prostheses used in Norway: a critical review of the literature from 1996-2000. Acta Orthop Scand 2004;75:663–76.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1080/00016470410004021&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=15762255&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000226050700003&link_type=ISI) 

6.  Ng CY, Ballantyne JA, Brenkel IJ. Quality of life and functional outcome after primary total hip replacement: a five-year follow-up. J Bone Joint Surg Br 2007;89:868–73.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1302/0301-620X.89B7.18482&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=17673577&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

7.  Woolhead GM, Donovan JL, Dieppe PA. Outcomes of total knee replacement: a qualitative study. Rheumatology (Oxford) 2005;44:1032–7.
    
    [Abstract/FREE Full Text](http://bmjopen.bmj.com/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTI6InJoZXVtYXRvbG9neSI7czo1OiJyZXNpZCI7czo5OiI0NC84LzEwMzIiO3M6NDoiYXRvbSI7czoyNToiL2Jtam9wZW4vMi8xL2UwMDA0MzUuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9) 

8.  Judge A, Cooper C, Williams S, et al. Patient-reported outcomes one year after primary hip replacement in a European Collaborative Cohort. Arthritis Care Res (Hoboken) 2010;62:480–8.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1002/acr.20038&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=20391502&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000280979400008&link_type=ISI) 

9.  Bellamy N, Buchanan WW, Goldsmith CH, et al. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15:1833–40.
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=3068365&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=A1988R854800020&link_type=ISI) 

10. Dreinhofer KE, Dieppe P, Sturmer T, et al. Indications for total hip replacement: comparison of assessments of orthopaedic surgeons and referring physicians. Ann Rheum Dis 2006;65:1346–50.
    
    [Abstract/FREE Full Text](http://bmjopen.bmj.com/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6ImFubnJoZXVtZGlzIjtzOjU6InJlc2lkIjtzOjEwOiI2NS8xMC8xMzQ2IjtzOjQ6ImF0b20iO3M6MjU6Ii9ibWpvcGVuLzIvMS9lMDAwNDM1LmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==) 

11. Jha AK, Orav EJ, Zheng J, et al. Patients' perception of hospital care in the United States. N Engl J Med 2008;359:1921–31.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1056/NEJMsa0804116&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=18971493&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000260454500008&link_type=ISI) 

12. Darzi A. High Quality Care for All: NHS Next Stage Review Final Report. London: Department of Health, 2008.
    
    

13. Guidance on the routine collection of Patient Reported Outcome Measures (PROMs). London: Department of Health, 2009.
    
    

14. Bachmeier CJ, March LM, Cross MJ, et al. A comparison of outcomes in osteoarthritis patients undergoing total hip and knee replacement surgery. Osteoarthritis Cartilage 2001;9:137–46.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1053/joca.2000.0369&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=11330253&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000167415400007&link_type=ISI) 

15. Murray DW, Britton AR, Bulstrode CJ. Loss to follow-up matters. J Bone Joint Surg Br 1997;79:254–7.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1302/0301-620X.79B2.6975&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=9119852&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

16. Konig A, Schreiber B, Rader C, et al. A comparison of knee and function score of patients lost to follow-up with patients reattending a prospective total knee arthroplasty study (In German). Z Orthop Ihre Grenzgeb 1999;137:57–60.
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=10327563&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

17. Kim J, Lonner JH, Nelson CL, et al. Response bias: effect on outcomes evaluation by mail surveys after total knee arthroplasty. J Bone Joint Surg Am 2004;86:15–21.
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=14711940&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

18. Kwon SK, Kang YG, Chang CB, et al. Interpretations of the clinical outcomes of the nonresponders to mail surveys in patients after total knee arthroplasty. J Arthroplasty 2010;25:133–7.
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=19106032&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000277580800026&link_type=ISI) 

19. Stroup DF, Berlin JA, Morton SC, et al. Meta-analysis of observational studies in epidemiology: a proposal for reporting. JAMA 2000;283:2008–12.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1001/jama.283.15.2008&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=10789670&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000086436600037&link_type=ISI) 

20. Roberts VI, Esler CN, Harper WM. A 15-year follow-up study of 4606 primary total knee replacements. J Bone Joint Surg Br 2007;89:1452–6.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.2106/JBJS.F.01328&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=17998180&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

21. Higgins J, Green S. Cochrane Handbook for Systematic Reviews of Interventions. The Cochrane Collaboration. 2011. [http://www.cochrane-handbook.org/](http://www.cochrane-handbook.org/) (accessed 21 Dec 2011).
    
    

22. Mullan RJ, Flynn DN, Carlberg B, et al. Systematic reviewers commonly contact study authors but do so with limited rigor. J Clin Epidemiol 2009;62:138–42.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1016/j.jclinepi.2008.08.002&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=19013767&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000262574100005&link_type=ISI) 

23. Nikolajsen L, Brandsborg B, Lucht U, et al. Chronic pain following total hip arthroplasty: a nationwide questionnaire study. Acta Anaesthesiol Scand 2006;50:495–500.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1111/j.1399-6576.2006.00976.x&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=16548863&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000236069900013&link_type=ISI) 

24. Jones CA, Voaklander DC, Johnston DW, et al. Health related quality of life outcomes after total hip and knee arthroplasties in a community based population. J Rheumatol 2000;27:1745–52.
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=10914862&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000088007600030&link_type=ISI) 

25. Quintana JM, Escobar A, Arostegui I, et al. Health-related quality of life and appropriateness of knee or hip joint replacement. Arch Intern Med 2006;166:220–6.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1001/archinte.166.2.220&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=16432092&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000234769400013&link_type=ISI) 

26. Nilsdotter AK, Petersson IF, Roos EM, et al. Predictors of patient relevant outcome after total hip replacement for osteoarthritis: a prospective study. Ann Rheum Dis 2003;62:923–30.
    
    [Abstract/FREE Full Text](http://bmjopen.bmj.com/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6ImFubnJoZXVtZGlzIjtzOjU6InJlc2lkIjtzOjk6IjYyLzEwLzkyMyI7czo0OiJhdG9tIjtzOjI1OiIvYm1qb3Blbi8yLzEvZTAwMDQzNS5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

27. Singh JA, Lewallen D. Predictors of pain and use of pain medications following primary Total Hip Arthroplasty (THA): 5,707 THAs at 2-years and 3,289 THAs at 5-years. BMC Musculoskelet Disord 2010;11:90.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1186/1471-2474-11-90&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=20462458&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

28. Wylde V, Hewlett S, Learmonth ID, et al. Persistent pain after joint replacement: prevalence, sensory qualities, and postoperative determinants. Pain 2011;152:566–72.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1016/j.pain.2010.11.023&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=21239114&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000287192200018&link_type=ISI) 

29. Baker PN, van der Meulen JH, Lewsey J, et al; National Joint Registry for England and Wales. The role of pain and function in determining patient satisfaction after total knee replacement. Data from the National Joint Registry for England and Wales. J Bone Joint Surg Br 2007;89:893–900.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1302/0301-620X.89B7.19091&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=17673581&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

30. Núñez M, Núñez E, del Val JL, et al. Health-related quality of life in patients with osteoarthritis after total knee replacement: factors influencing outcomes at 36 months of follow-up. Osteoarthritis Cartilage 2007;15:1001–7.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1016/j.joca.2007.02.019&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=17428689&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000249983200002&link_type=ISI) 

31. Stephens MA, Druley JA, Zautra AJ. Older adults' recovery from surgery for osteoarthritis of the knee: psychosocial resources and constraints as predictors of outcomes. Health Psychol 2002;21:377–83.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1037/0278-6133.21.4.377&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=12090680&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000176373800008&link_type=ISI) 

32. Lundblad H, Kreicbergs A, Jansson KA. Prediction of persistent pain after total knee replacement for osteoarthritis. J Bone Joint Surg Br 2008;90:166–71.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1302/0301-620X.90B2.19640&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=18256082&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

33. Nilsdotter AK, Toksvig-Larsen S, Roos EM. Knee arthroplasty: are patients' expectations fulfilled? A prospective study of pain and function in 102 patients with 5-year follow-up. Acta Orthop 2009;80:55–61.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1080/17453670902805007&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=19234886&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000264347300012&link_type=ISI) 

34. Vuorenmaa M, Ylinen J, Kiviranta I, et al. Changes in pain and physical function during waiting time and 3 months after knee joint arthroplasty. J Rehabil Med 2008;40:570–5.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.2340/16501977-0213&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=18758675&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000257951300011&link_type=ISI) 

35. Czurda T, Fennema P, Baumgartner M, et al. The association between component malalignment and post-operative pain following navigation-assisted total knee arthroplasty: results of a cohort/nested case-control study. Knee Surg Sports Traumatol Arthrosc 2010;18:863–9.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1007/s00167-009-0990-y&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=19946667&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000278931500003&link_type=ISI) 

36. Brander VA, Stulberg SD, Adams AD, et al. Predicting total knee replacement pain: a prospective, observational study. Clin Orthop Relat Res 2003;416:27–36.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1097/01.blo.0000092983.12414.e9&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=14646737&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

37. Lucht U. The Danish Hip Arthroplasty Register. Acta Orthop Scand 2000;71:433–9.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1080/000164700317381081&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=11186396&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000165329900001&link_type=ISI) 

38. Puhan M, Soesilo I, Guyatt G, et al. Combining scores from different patient reported outcome measures in meta-analyses: when is it justified? Health Qual Life Outcomes 2006;4:94.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1186/1477-7525-4-94&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=17156420&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

39. Kane RL, Saleh KJ, Wilt TJ, et al. The functional outcomes of total knee arthroplasty. J Bone Joint Surg Am 2005;87:1719–24.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.2106/JBJS.D.02714&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=16085610&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

40. Ethgen O, Bruyere O, Richy F, et al. Health-related quality of life in total hip and total knee arthroplasty: a qualitative and systematic review of the literature. J Bone Joint Surg Am 2004;86-A:963–74.
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=15118039&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

41. Bourne RB, Chesworth BM, Davis AM, et al. Patient satisfaction after total knee arthroplasty: who is satisfied and who is not? Clin Orthop Relat Res 2010;468:57–63.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1007/s11999-009-1119-9&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=19844772&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000274767200010&link_type=ISI) 

42. MacKichan F, Wylde V, Dieppe P. The assessment of musculoskeletal pain in the clinical setting. Rheum Dis Clin North Am 2008;34:311–30.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1016/j.rdc.2008.03.002&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=18638679&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

43. Hawker GA, Stewart L, French MR, et al. Understanding the pain experience in hip and knee osteoarthritis - an OARSI/OMERACT initiative. Osteoarthritis Cartilage 2008;16:415–22.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1016/j.joca.2007.12.017&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=18296075&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000255194100003&link_type=ISI) 

44. Hawker G, Wright J, Coyte P, et al. Health-related quality of life after knee replacement. Results of the knee replacement patient outcomes research team study. J Bone Joint Surg Am 1998;80:163–73.
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=9486722&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

45. Rolfson O, Dahlberg LE, Nilsson JA, et al. Variables determining outcome in total hip replacement surgery. J Bone Joint Surg Br 2009;91:157–61.
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=19190046&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

46. Dohnke B, Knäuper B, Müller-Fahrnow W. Perceived self-efficacy gained from, and health effects of, a rehabilitation program after hip joint replacement. Arthritis Rheum 2005;53:585–92.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1002/art.21324&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=16082655&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000231041900017&link_type=ISI) 

47. Jones CA, Beaupre LA, Johnston DW, et al. Total joint arthroplasties: current concepts of patient outcomes after surgery. Rheum Dis Clin North Am 2007;33:71–86.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1016/j.rdc.2006.12.008&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=17367693&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

48. Ackerman IN, Bennell KL. Does pre-operative physiotherapy improve outcomes from lower limb joint replacement surgery? A systematic review. Aust J Physiother 2004;50:25–30.
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=14987189&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000220383000004&link_type=ISI) 

49. McDonald S, Hetrick SE, Green S. Pre-operative education for hip or knee replacement. Cochrane Database Syst Rev 2004;(1):CD003526.
    
    

50. Minns Lowe CJ, Barker KL, Dewey M, et al. Effectiveness of physiotherapy exercise after knee arthroplasty for osteoarthritis: systematic review and meta-analysis of randomised controlled trials. BMJ 2007;335:812–15.
    
    [Abstract/FREE Full Text](http://bmjopen.bmj.com/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MzoiYm1qIjtzOjU6InJlc2lkIjtzOjEyOiIzMzUvNzYyNC84MTIiO3M6NDoiYXRvbSI7czoyNToiL2Jtam9wZW4vMi8xL2UwMDA0MzUuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9) 

51. Minns Lowe CJ, Barker KL, Dewey ME, et al. Effectiveness of physiotherapy exercise following hip arthroplasty for osteoarthritis: a systematic review of clinical trials. BMC Musculoskelet Disord 2009;10:98.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1186/1471-2474-10-98&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=19653883&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 

52. Khan F, Ng L, Gonzalez S, et al. Multidisciplinary rehabilitation programmes following joint replacement at the hip and knee in chronic arthropathy. Cochrane Database Syst Rev 2008;(2):CD004957.
    
    

53. Kalkman CJ, Visser K, Moen J, et al. Preoperative prediction of severe postoperative pain. Pain 2003;105:415–23.
    
    [CrossRef](http://bmjopen.bmj.com/lookup/external-ref?access_num=10.1016/S0304-3959(03)00252-5&link_type=DOI) 
    
    [PubMed](http://bmjopen.bmj.com/lookup/external-ref?access_num=14527702&link_type=MED&atom=%2Fbmjopen%2F2%2F1%2Fe000435.atom) 
    
    [Web of Science](http://bmjopen.bmj.com/lookup/external-ref?access_num=000186085500005&link_type=ISI)