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Original research
Prevalence of and factors associated with osteoarthritis and pain in retired Olympians compared with the general population: part 1 – the lower limb
  1. Debbie Palmer1,2,
  2. Dale Cooper3,
  3. Jackie L Whittaker4,5,
  4. Carolyn Emery6,
  5. Mark E Batt7,8,
  6. Lars Engebretsen9,10,
  7. Patrick Schamasch11,
  8. Malav Shroff11,
  9. Torbjørn Soligard10,
  10. Kathrin Steffen9,
  11. Richard Budgett10
  1. 1Edinburgh Sports Medicine Research Network, Institute for Sport PE and Health Sciences, The University of Edinburgh, Edinburgh, UK
  2. 2School of Medicine, University of Nottingham, Nottingham, UK
  3. 3School of Allied Health Professions, Keel University, Keele, UK
  4. 4Department of Physical Therapy, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada
  5. 5Arthritis Research Canada, Richmond, British Columbia, Canada
  6. 6Sport Injury Prevention Research Centre, Faculty of Kinesiology and Departments of Paediatrics and Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
  7. 7Nottingham University Hospitals NHS Trust, Nottingham, UK
  8. 8Centre for Sport, Exercise and Osteoarthritis Versus Arthritis, Queen's Medical Centre, Nottingham, UK
  9. 9Department of Sports Medicine, Oslo Sports Trauma Research Center, Norwegian School of Sport Sciences, Oslo, Norway
  10. 10Medical and Scientific Department, International Olympic Committee, Lausanne, Switzerland
  11. 11Medical Committee, World Olympians Association, Lausanne, Switzerland
  1. Correspondence to Dr Debbie Palmer, Edinburgh Sports Medicine Research Network, Institute for Sport, PE and Health Sciences, The University of Edinburgh, Edinburgh, UK; dpalmer{at}ed.ac.uk

Abstract

Objectives This study aims (1) to determine the prevalence of lower limb osteoarthritis (OA) and pain in retired Olympians; (2) to identify factors associated with their occurrence and (3) to compare with a sample of the general population.

Methods 3357 retired Olympians (median 44.7 years) and 1735 general population controls (40.5 years) completed a cross-sectional survey. The survey captured demographics, general health, self-reported physician-diagnosed OA, current joint/region pain and injury history (lasting >1 month). Adjusted OR (aOR) compared retired Olympians with the general population.

Results The prevalence of (any joint) OA in retired Olympians was 23.2% with the knee most affected (7.4%). Injury was associated with increased odds (aOR, 95% CI) of OA and pain in retired Olympians at the knee (OA=9.40, 6.90 to 12.79; pain=7.32, 5.77 to 9.28), hip (OA=14.30, 8.25 to 24.79; pain=9.76, 6.39 to 14.93) and ankle (OA=9.90, 5.05 to 19.41; pain=5.99, 3.84 to 9.34). Increasing age and obesity were also associated with knee OA and pain. While the odds of OA did not differ between Olympians and the general population, Olympians with prior knee and prior hip injury were more likely than controls with prior injury to experience knee (1.51, 1.03 to 2.21 (Olympians 22.0% vs controls 14.5%)) and hip OA (4.03, 1.10 to 14.85 (Olympians 19.1% vs Controls 11.5%)), respectively.

Conclusions One in four retired Olympians reported physician-diagnosed OA, with injury associated with knee, hip and ankle OA and pain. Although overall OA odds did not differ, after adjustment for recognised risk factors Olympians were more likely to have knee and hip OA after injury than the general population, suggesting injury is an occupational risk factor for retired Olympians.

  • Osteoarthritis
  • Hip
  • Knee
  • Ankle
  • Sporting injuries

Data availability statement

All data relevant to the study are included in the article or uploaded as online supplemental information.

http://creativecommons.org/licenses/by-nc/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/bjsports-2021-104762

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    WHAT IS ALREADY KNOWN ON THIS TOPIC

    • Elite sport participation can lead to an increased risk of injury, and there is an emerging evidence from retired athlete studies of an association between injury, ongoing pain and osteoarthritis.

    WHAT THIS STUDY ADDS

    • One in four retired Olympians reported physician-diagnosed osteoarthritis (OA), and injury was associated with an increased risk of OA and pain at the knee, hip and ankle. The odds of knee and hip OA after prior injury were significantly greater for Olympians compared with the general population.

    HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

    • Primary injury prevention should be a continued focus for elite athlete medical and coaching teams with particular focus on the prevention of significant knee and hip injuries. Approaches to athlete injuries should ensure full and complete rehabilitation of injuries, with a biopsychosocial approach and discussion of long-term risks to inform athlete behaviours during and after injury.

    Introduction

    Elite sport participation can lead to an increased risk of injury, with injuries to the knee, lumbar spine, shoulder and ankle reported to be most frequent and also among the most severe in Olympic athletes.1–4 Even after acute symptoms have resolved athletes frequently report ongoing pain and dysfunction for years after an initial injury.4

    Significant joint injury is a risk factor for future osteoarthritis (OA), and there is an emerging body of evidence in retired athletes from football (soccer),5–7 Rugby Union8 and from Olympic sports9–11 reporting an association between joint injury and ongoing pain, and the development and progression of OA. In order to truly understand the magnitude of the problem it is important to understand if and how Olympians differ compared with the general population.12 To date, few retired-athlete studies have included these comparisons, and where comparisons to a general population control are made, they are limited to a single sex, specific sport or geographical region.5 7–10

    In addition, many studies focus on isolated body joints such as the hip or knee,7 10 11 however, the natural history of OA varies, with factors contributing to disease occurrence and progression appearing to be joint specific.13–17 For example, around 8% of hip and 12% of knee OA are reported to be post-traumatic (due to injury),13 15 compared with almost 80% for ankle OA.18 19 Hip OA has been shown to progress more rapidly in women than in men but with no gender effect observed on progression of knee OA.20 21 Hence, it is important that we understand the joint-specific response to different stimuli including injury, across multiple body sites. Therefore, we aimed (1) to determine the prevalence of lower limb self-reported physician-diagnosed OA and pain in retired Olympians, (2) to identify factors associated with lower limb OA and pain in retired Olympians and (3) to make comparisons with a sample of the general population. A similar detailed study describing the factors associated with spine and upper limb OA and pain are reported separately in part 2.

    Methods

    This cross-sectional study collected self-report data from retired Olympians and general population controls using an online questionnaire available in eight languages (English, French, German, Spanish, Russian, Chinese, Japanese and Korean). Data collection was conducted between April 2018 and June 2019. Retired Olympians were those who had competed in at least one summer and/or winter Olympic Games, who were aged 16 years of age or older, and considered themselves retired from Olympic level training and competition. General population controls in this study were any individuals who had not competed at a summer and/or winter Olympic Games, who were 16 years of age or older.

    Recruitment

    The survey was promoted to retired Olympians Globally through World Olympians Association (WOA) and IOC communication platforms. Those wishing to participate were asked to register with the WOA OLY database. A survey link was then emailed to all Olympians on the database. Additionally, the WOA engaged with National Olympians Associations (NOA) who direct emailed the survey to their countries Olympians.4 The researchers are unaware how many Olympians NOA promotions reached, it is also unknown how many of the 14 300 Olympians on the OLY database were active and how many were retired, hence it is not possible to calculate a retired Olympian response rate. The general population control group recruitment was conducted in three phases: (1) through study promotion globally through WOA and IOC communication platforms; (2) by members of the research group through their own academic and industry organisations and their local regional public leisure, medical and community centres (the latter via posters) and (3) using Olympian ‘buddies’ where at the end of their survey Olympians were asked to recruit a non-Olympian friend.

    Detailed study information, including information on data handling and confidentiality, was provided at the start of the survey. We explicitly outlined that by completing and submitting the questionnaire, participants were consenting to their information being used anonymously for the study.

    Questionnaire survey

    The questionnaire was an online web-based survey hosted by SurveyMonkey. The Olympian survey was password protected while the general population survey was open.4 The survey contained four main sections: (1) baseline demographics, (2) sport participation and self-reported injury history details, (3) self-reported current musculoskeletal health and (4) current general health and quality of life.

    Baseline questions requested demographics including age, sex, country of residence, and current height (cm) and weight (kg) which were used to calculate body mass index (BMI, kg/m2). Injury history questions asked participants to recall all significant injuries (lasting >1 month) occurring at any time during sport, exercise or other activities, including the injury anatomical location, mechanism (eg, recurrence) and treatment. Significant ‘injury’ was defined as ’any injury causing significant pain and/or dysfunction for a period of 1 month (or more)’.4

    The questionnaire captured information on participants current musculoskeletal health. The presence of joint pain was established using a validated question ‘Do you currently experience pain, for most days of the last month, in this joint’,22 which was also modified to record joint stiffness. Self-reported physician-diagnosed OA was ascertained by asking ‘Have you ever been diagnosed with OA in any of your joints by a medical professional'.11 History of joint surgery including type of surgery, for example, joint replacement, was also recorded. Constitutional (in their 20s—if aged over 30) and current knee alignment were assessed using a validated drawing,22 and classified as either normal, varus or valgus (mild and severe combined). The presence of nodal OA was determined using a validated diagram.23 Nodal OA was present if finger nodes were reported in at least 2 rays of both hands. Additional questions on general health asked about the presence of co-morbidities for example, heart disease or diabetes.

    Patient and public involvement

    A patient advisory group of nine retired Olympians provided input in the face validation of the questionnaire content and design, focusing on question understanding and clarity and overall questionnaire length and acceptability. Comments from the patient advisory group were incorporated into the final version of the survey.

    Statistical analysis

    Descriptive statistics were presented as frequencies (proportion) for categorical variable, and mean and SD for continuous variables. Prevalence was calculated dividing the number of participants with the outcome of interest by the total number of participants and presented as percentage (%) with 95% CIs. To determine if distributions of variables were statistically different between Olympians and the general population continuous variables were analysed by using independent t-tests, or Mann-Whitney U test, and categorical variables by the χ2 test as appropriate. Significance was accepted at p<0.05. The prevalences of the primary outcome variables OA and pain were calculated for each lower limb joint (hip, knee, ankle). If bilateral, the most severe joint was selected as the index joint for analysis. Logistic regression was used to estimate odd ratios (with 95% CI) of each primary outcome for each independent variable, and odds ratios were adjusted (aOR) in a multivariable model for a priori age, BMI, sex and injury, for Olympians. A separate model was used to assess putative risk factors for each primary outcome comparing Olympians versus general population controls, followed by stage adjustment for age, BMI, sex; and age, BMI, sex and injury. Independent variables with fewer than five events per variable were excluded.24 25 Age and BMI were non-linear and so were categorised according to previous research.7 11 22 Significant injuries were matched according to the index joint and included if they preceded OA diagnosis or episode of pain in that joint. Where there was colinearity (eg, aORs for OA associated with injury) variables were removed. Imputation was not undertaken for occasional missing values. Analysis was conducted using Stata IC V.16.

    A power calculation was conducted based on an estimated prevalence of 7% knee OA in a similar aged general population (median 45 years).26 With a 2:1 ratio of exposed (Olympians) and unexposed (general population), this study had at least 80% power at 0.05 to detect an OR of 1.32 or greater based on a total sample of 5062 (calculation conducted using GPower V.3.1.9.7).7 11

    Results

    Descriptive characteristics

    At the close of the survey, there were 4745 Olympian and 2462 general population entries. A total of 1388 Olympian and 727 general population ineligible (ie, blank, incomplete, duplicate) entries were removed leaving 3357 Olympian (from 131 countries) and 1735 general population (73 countries) completed questionnaires for data analysis.

    The median age of Olympians was 44.7 years (range 16–97) with 45% female (and 55% male) while the comparison general population controls were aged 40.5 years (range 16–88) with 58% female (and 42% male) (table 1). Retired Olympians reported a higher prevalence of injury (68.5% vs 60.5%), recurrent injury (41.5% vs 30.7%), and OA (in any joint) (23.2% vs 15.7%) and pain (41.3% vs 37.8%) compared with the general population.

    View this table:
    Table 1

    Anthropometric, injury, joint health and constitutional factors for Olympians and general population controls

    Prevalence of OA by body joint/region

    The prevalence of self-reported physician-diagnosed OA was highest for the knee (Olympians 7.4% vs controls 5.5%; p=0.011), followed by the lumbar spine (5.7% vs 3.8%; p=0.004), hip (3.3% vs 2.1%; p=0.011), shoulder (2.4% vs 1.3%; p=0.008) and cervical spine (2.3% vs 1.4%; p=0.04) but similar for the ankle (1.1% vs 1.1%; p=0.982) (figure 1). Among the most common sites for OA, data from this point forwards are presented for the lower limb.

    Figure 1
    Figure 1

    OA prevalence (with 95% CI) by body joint/region for Olympians and general population controls. OA, osteoarthritis.

    Lower limb OA in Olympians

    Table 2 presents the prevalence and adjusted odds for factors associated with self-reported knee, hip and ankle OA in Olympians. The odds of OA were associated with increasing age at the knee (40–59 years aOR 2.44 (95% CI 1.66 to 3.60) and >60 years aOR 5.67 (95% CI 3.66 to 8.79) and hip (40–59 years aOR 2.41 (95% CI 1.35 to 4.32) and >60 years aOR 6.75 (95% CI 3.64 to 12.53)). Female sex (aOR 1.88 (95% CI 1.37 to 2.58)) and obesity (aOR 1.67 (95% CI 1.05 to 2.63)) were also associated with greater odds of knee OA. Prior knee injury was significantly associated with greater odds of knee OA (aOR 9.40 (95% CI 6.90 to 12.79)), and the same was observed for prior hip injury and hip OA, and for the ankle. Recurrent knee injury was also associated with knee OA (aOR 2.40 (95% CI 1.63 to 3.53)). Factors associated with knee, hip and ankle OA in the general population are presented in online supplemental appendices 1–3, respectively.

    View this table:
    Table 2

    Factors associated with lower limb OA in Olympians

    Lower limb pain in Olympians

    Table 3 presents the prevalence of and aOR for factors associated with self-reported pain at the knee, hip and ankle in Olympians. Pain was associated with increasing age for the knee (>60 years aOR 1.99 (95% CI 1.41 to 2.80)) and hip (aOR 1.78 (95% CI 1.13 to 2.82)). For the ankle the odds of pain did not change by age. Overweight (aOR 1.48 (95% CI 1.12 to 1.95)) and obesity (aOR 2.34 (95% CI 1.63 to 3.37)) were associated with increased odds of pain at the knee. Prior knee injury was significantly associated with knee pain (aOR 7.32 (95% CI 5.77 to 9.28)), and the same was observed for the hip and ankle. Recurrent knee injury and recurrent ankle injury were also associated with greater odds of pain at the knee (2.33 aOR (95% CI 1.67 to 3.26)) and ankle (3.88 aOR (95% CI 1.75 to 8.61)). The prevalence and odds for factors associated with knee, hip and ankle pain in the general population are presented in online supplemental appendices 4–6 respectively.

    View this table:
    Table 3

    Factors associated with lower limb pain in Olympians

    Lower limb OA in Olympians versus controls

    Overall, after adjusting for covariates the odds of knee OA (aOR 1.17 (95% CI 0.88 to 1.54) and hip OA (aOR 1.43 (95% CI 0.93 to 2.20) were not significantly different in retired Olympians compared with general population controls (table 4). However, the odds of experiencing knee OA were greater for Olympians compared with the general population after prior knee injury (prevalence 22.0% vs 14.5%, aOR 1.51 (95% CI 1.03 to 2.21)) and after recurrent knee injury (30.6% vs 17.4%, aOR 1.86 (95% CI 1.06 to 3.26)). The odds of self-reported hip OA after hip injury were also greater for Olympians compared with the general population controls (prevalence 19.1% vs 11.5%, aOR 4.03 (95% CI 1.10 to 14.85)). There were no differences observed between Olympians and the general population for ankle OA (online supplemental appendix 7).

    View this table:
    Table 4

    Odds of lower limb OA for Olympians versus a general population control

    Lower limb pain in Olympians versus controls

    The odds of knee and hip pain when adjusting for covariates (age, sex, BMI and injury) were not significantly different in retired Olympians in comparison to the general population controls (table 5). While the prevalence of knee and hip pain associated with injury was higher for Olympians compared with the general population (31.7% vs 24.4% and 30.9% vs 19.7%, respectively) the odds were not significant (knee aOR 1.34 (95% CI 0.98 to 1.83); hip aOR 1.63 (95% CI 0.77 to 3.49)). There were no differences observed between Olympians and the general population for ankle pain (online supplemental appendix 8).

    View this table:
    Table 5

    Odds of lower limb pain for Olympians versus a general population control

    Discussion

    This is the first worldwide study comparing the factors associated with self-reported lower limb OA and pain in retired Olympians, with comparison to the general population. The main findings were as follows: (1) one in four retired Olympians reported having physician-diagnosed OA in any joint, with the knee, hip and ankle among the most common sites for OA; (2) injury was associated with increased odds of self-reported OA and pain in the knee, hip, and ankle in Olympians; (3) the odds of lower limb OA and pain did not differ between Olympians and control and (4) however, after significant injury, the odds of knee and hip OA were higher for Olympians compared with the general population.

    OA and pain

    The prevalence of knee OA (7.5%) among our global cohort of retired Olympians was lower compared with previous retired athlete studies in footballers (28%), cricketers (22%) and Great Britain (GB) Olympians (14%). The prevalence of hip OA (cricketers 8%, GB Olympians 11%) and ankle OA (cricketers 4.0%) were also lower.7 11 27 A similar pattern was observed for lower limb pain where knee, hip and ankle pain were lower compared with previous reported rates.7 11 27 Some of the differences observed are likely influenced by the multisport nature of the current cohort and inclusion of a large proportion of athletes from sports characterised by few contact events and acute traumatic injuries—known risk factors for OA—such as swimming, rowing, sailing and shooting.4 28 In addition, the current cohort was younger (45 years) compared with other retired athlete studies (59–64 years),7 11 27 and increasing age is known to be associated with higher rates of pain and OA,26 a finding also present in our study. OA rates may also be influenced by the instrument of measurement, for example, rates of radiographic established knee OA such as that used by Fernandes et al7 may be higher than self-reported physician-diagnosed OA due to the discordance between radiographic findings and symptomatic disease.29

    When comparing Olympians with the general population in this study the prevalence of OA and pain at the hip and knee were higher, similar to previous retired athlete study findings.5 7 9 28 However, when adjusting for covariates between the groups there was no difference in the odds of experiencing OA and pain. This is in contrast to findings reported previously in retired footballers who found higher odds of knee pain and OA when compared with the general population.5 7 For the ankle, there was no difference in pain and OA between Olympians and controls in agreement with findings observed for ankle pain and OA in former Greek footballers (vs controls).30

    Factors associated with lower limb OA

    Across the lower limb the odds of self-reported OA in retired Olympians were higher after significant joint injury (lasting 1 month or more). For example, 22% of Olympians in this study who reported having a significant prior knee injury reported knee OA compared with just 3.1% reporting knee OA with no prior knee injury (aOR 9.40). A similar pattern was also observed for the hip and ankle. Previous retired athlete studies have shown injury is a risk factor for OA at the hip, knee6 7 11 31 32 and ankle6 and this study adds weight to this association. Overall, the risk of injury-related OA in this study is greater than previously reported in retired elite German female footballers (knee aOR 1.32; ankle 1.13),6 English male professional footballers (knee aOR 2.88)32 and GB Olympians (knee aOR 4.40 and hip 1.61).11 The reasons for the differences observed are unclear, but may be due to geographical and/or sport (type and single vs multi) related factors,11 32 and level and intensity of sport participation.12 33 34 Of concern, this study cohort was younger than the English footballer and GB Olympian cohorts, and so the magnitude of this injury-related risk may increase further as this population ages.35 36 Recurrent injury was also associated with greater odds of knee OA in retired Olympians, which supports findings by Parekh et al32 who identified an injury dose response for radiographic knee OA in ex professional footballers whereby subsequent injuries after the index injury increased the odds of knee OA.

    The association between injury and OA in retired Olympians in this study may be unsurprising given previous injury is also a known risk factor for OA at the knee,37–39 hip13 37 and ankle16 18 in the general population. While the overall odds of lower limb OA did not differ when comparing retired Olympians with the general population in this study, Olympians were one and a half times more likely to have knee OA after knee injury, and two times more likely to have knee OA after recurrent knee injury. They were also four times more likely to have hip OA after hip injury. Meaning knee and hip injuries, and recurrent knee injuries, in Olympians may have greater consequences with respect to the onset of self-reported OA in those joints, compared with similar injuries occurring in the general population. Few retired athlete studies reporting knee and hip OA have used comparisons with a general population control7 9 28 33 and none have directly compared the influence of injury on OA between these groups. Fernandes et al reported higher prevalence and odds of knee OA in male retired footballers compared with men in the general population with the authors stating that knee injury was the main attributable risk factor.7 32

    The nature and intensity of sport participation may influence the frequency and severity of injuries in elite athletes, when compared with the general population, and in this study the prevalence of significant injury (lasting 30 days or more) was higher for retired Olympians. The type of injury may also be a contributing factor. For example, injuries that directly damage articular cartilage or lead to instability (eg, ACL injuries) are known to precipitate OA onset and injuries of greater severity known to accelerate the onset and progression of OA.19 40–43 Knee lesion of meniscus/cartilage and knee ligament rupture injuries were among the most common injuries reported by Olympians in this study.4 In addition, athlete behaviours and treatments during injury where there is pressure to return quickly from injury may be influencing outcomes. For example, three-quarters of Olympians in this study indicated that they put pressure on themselves to return to sport, with a quarter continuing all training/competition activities, when experiencing injury.4 Continuing to compete while injured likely delays recovery,44 and the higher prevalence of recurrent injury in Olympians compared with the general population, and the greater odds of OA after recurrent injury, may be indicators of poor or incomplete rehabilitation and may also add weight to early findings of an injury-dose response for OA.32

    Factors associated with lower limb pain

    Similar to previous retired athlete studies, the odds of knee (aOR 7.72), hip (aOR9.76) and ankle (aOR 5.99) pain were significantly higher after prior injury in retired Olympians. This also confirms anecdotal findings from this study where Olympians attributed ongoing pain and functional limitation to sport-related injuries they had sustained.4 In a comparable study in retired GB Olympians, the odds of joint pain were also reported to be higher after joint injury at the knee and hip.11 Injury was also the strongest risk factor reported for knee pain in retired professional footballers.7 32 Recurrent knee and ankle injuries in this study were associated with a twofold and fourfold increase in knee and ankle pain, respectively, in retired Olympians. Similar to OA, pointing to a potential injury-dose pain response previously reported in retired footballers.32

    When comparing retired Olympians with the general population in this study, overall there were no differences observed between the groups for knee, hip or ankle pain. This was similar to findings for lower limb OA in this study and again in contrast to previous retired athlete studies who report higher rates of lower limb pain in retired athletes vs controls.5 7 28 While these findings are positive, interpretation should be made with caution. With the comparative young age of the present cohort, it will be important to understand if the magnitude of any current differences between retired Olympians and the controls changes over time.

    Clinical implications

    To be able to prevent long-term health complaints such as pain and OA in retired athlete populations, it is important to understand the different factors associated with joint specific responses. While some findings within this study are not significant it does not mean that they are not clinically meaningful. Results from this study indicate that current athlete injury management should allow wherever possible full and complete rehabilitation from significant index injuries athletes sustained during their careers, in particular injuries to the knee and hip. A multidisciplinary approach should include addressing athlete behaviours and treatments during injury, for example, pressure to return, depression, pain killer use and joint injections.4 Postretirement, targeted tertiary prevention strategies should also be employed. Female sex, and overweight and obesity are the risk factors for OA; they have been linked to higher rates of knee OA and knee pain in the general population, and knee (and hip) disability in former athletes,28 and were factors associated with knee pain and OA for Olympians in this study. Body weight is a potential modifiable risk factor, and numerous studies have shown reductions in BMI attenuate knee pain in patients with obesity and those with both obesity and knee OA.45 46 Greater weight loss can also precipitate greater reductions in pain.47 In the present cohort, BMI increased significantly from the time Olympians competed to post athletic career.4 Hence, targeted weight management advice and interventions for those with a prior history of significant knee and/or hip injury, may have the potential to reduce both symptomatic OA and pain in later life.46

    Strengths and limitations

    Previous retired athlete studies have focused on single sport, joint and sex, with few including comparisons to the general population.5 7–10 For the first time, this study presents factors associated with OA and pain across multiple joints of the lower limb in both male and female retired athletes globally, with comparison to the general population. While this study includes Olympian data across 42 summer and 15 winter Olympic sports as one homogeneous group, there is limited understanding of the influence individual Olympic sports may have on these risks. However, with pain and OA clearly associated with prior injury, and the wealth of previous research reporting the aetiology of injury for different sports,2–4 it can be anticipated that athletes participating in those sports with known higher prevalence of significant injuries to the knee, hip and ankle, including recurrent injuries, may be at increased risk.

    There are several limitations to this study. It is recognised that this cross-sectional study may be limited by recall bias, given the range of ages. To mitigate some recall bias a significant, 1 month, injury definition was used.4 Results presented in some categories may be affected by sparse data bias.48 While the authors were able to include known risk factors for OA and pain there may be unmeasured or unknown confounders influencing these outcomes, hence causal inferences should be made with caution. We cannot provide an accurate survey response rate as it was not possible to know how many retired Olympians study promotion reached.4 There are an estimated 100 000 Olympians worldwide today and around 20 000 current Olympians.2–4 Therefore, the present sample represents around 4% of the total retired Olympian population and our conclusions are limited to this sample. Finally, it is not clear if the control sample in this study are truly representative of the general population. Given that the control cohort were recruited from WOA and IOC social media, and via ’Olympian buddies’ it is not unlikely that this general population group were more interested in sport and consequently more active in sport and exercise than other comparison general population controls. If the current control cohort was more active in sport, they may also have reported higher rates of injury, which may explain some of the lack of difference observed between our two groups, when compared with significant differences found in other retired athlete studies.

    Conclusions

    In summary, injury was associated with an increased risk of OA and pain in the knee, hip and ankle in retired Olympians. Overall, the odds of OA and pain did not differ between Olympians and controls, however, the odds of knee and hip OA after prior injury were significantly higher for Olympians. These findings may be used to inform prevention strategies to reduce the risk of knee, hip and ankle OA and pain in Olympians after retirement from sport.

    Data availability statement

    All data relevant to the study are included in the article or uploaded as online supplemental information.

    Ethics statements

    Patient consent for publication

    Ethics approval

    This study involves human participants and was approved by Ethical approval for the study was obtained from Edinburgh Napier University (UK) ethics committee (SAS/00011) Participants gave informed consent to participate in the study before taking part.

    Acknowledgments

    We acknowledge the contribution and support of the World Olympians Association administration team throughout the different stages of the study including study promotion and participant recruitment. We would also like to offer thanks to the study survey languages translation checkers, Francis Bougie, Gillian Cameron, Ayako Ito, Toshinobu Kawai, Juwon Kim, Natalia Grek, Carlos Valiente Palazón, Ivory Wu and Valeriya Yanina. Finally, we would like to sincerely thank all of the Olympians and members of the general population who took the time and effort to complete the survey questions, without whose help this study would not have been possible.

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    Supplementary materials

    Footnotes

    • Twitter @DebbiePalmerOLY, @jwhittak_physio, @CarolynAEmery, @larsengebretsen, @TSoligard

    • Contributors All authors contributed to the study conception and design, data collection and interpretation. DP analysed the data and drafted the paper. All authors provided revisions and contributed to the final manuscript. DP is the guarantor.

    • Funding The World Olympians Association funded the Retired Olympian Musculoskeletal Health Study (ROMHS) with a research grant from the International Olympic Committee (IOC).

    • Competing interests TS works as scientific manager in the Medical and Scientific Department of the IOC. LE is Head of Scientific Activities in the Medical and Scientific Depart of the IOC. LE is Editor and KS coeditor of the British Journal of Sports Medicine-Injury Prevention and Health Protection. RB is director of the Medical and Scientific Department of the IOC.

    • Patient and public involvement Patients and/or the public were involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the Methods section for further details.

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

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.