{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T10:48:58Z","timestamp":1782730138756,"version":"3.54.5"},"reference-count":42,"publisher":"BMJ","issue":"3","license":[{"start":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T00:00:00Z","timestamp":1773273600000},"content-version":"unspecified","delay-in-days":11,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000272","name":"National Institute for Health and Care Research","doi-asserted-by":"publisher","award":["NIHR303317"],"award-info":[{"award-number":["NIHR303317"]}],"id":[{"id":"10.13039\/501100000272","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open"],"accepted":{"date-parts":[[2026,2,26]]},"published-print":{"date-parts":[[2026,3]]},"abstract":"<jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>\n                      People with body mass index (BMI) \u226535 kg\/m\n                      <jats:sup>2<\/jats:sup>\n                      have an approximately 19-fold increased risk of undergoing total knee replacement (TKR); however, many UK integrated care boards (37%) have restrictive policies which limit access to TKR for people based on BMI. Therefore, access to both surgical and non-surgical treatments varies widely, exacerbating existing health inequalities. It remains unclear how decisions about offering TKR are made in people with severe knee osteoarthritis, which weight-loss interventions are provided in practice and how different management pathways relate to patient outcomes among individuals with high BMI.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods and analysis<\/jats:title>\n                    <jats:p>This study will recruit 400 participants with severe Kellgren-Lawrence grade four knee osteoarthritis from eight secondary care centres in England. All participants, irrespective of BMI, will provide baseline clinical data and patient-reported outcome measures (PROMs), enabling characterisation of baseline associations between BMI, knee function and body image.<\/jats:p>\n                    <jats:p>\n                      A prespecified subgroup of participants with BMI \u226535 kg\/m\n                      <jats:sup>2<\/jats:sup>\n                      (minimum n=105) will undergo longitudinal follow-up at 6 months, 12 months and 24\u2009months, including repeat BMI measurement, PROMs and detailed data on access to surgical and non-surgical interventions, including weight-loss strategies and TKR. For those with BMI \u226535 kg\/m\n                      <jats:sup>2<\/jats:sup>\n                      , statistical modelling will be used to explore associations between baseline factors and longitudinal outcomes including Oxford Knee Score and weight change at 12\u2009months (n\u2265105). Structural equation modelling will be used to quantify associations between BMI and knee pain\/function mediated by psychosocial factors using data from all participants (n=400). A nested qualitative study of surgeons and patients will explore obstacles and preferences in the management of severe knee osteoarthritis.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Ethics and dissemination<\/jats:title>\n                    <jats:p>The study received ethical approval from the West of Scotland REC 5 (Ref: 24\/WS\/0146) on 10 October 2024. Results will be disseminated through peer-reviewed publications.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Trial registration number<\/jats:title>\n                    <jats:p>\n                      <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"isrctn\" xlink:href=\"ISRCTN42984928\">ISRCTN42984928<\/jats:ext-link>\n                      .\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjopen-2025-112478","type":"journal-article","created":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T15:58:02Z","timestamp":1773331082000},"page":"e112478","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Obesity and arthritis of the knee Study (OAKS): study protocol for a prospective cohort study examining the treatments and outcomes of people with obesity and severe knee arthritis"],"prefix":"10.1136","volume":"16","clinical-trial-number":[{"clinical-trial-number":"isrctn42984928","registry":"10.18810\/isrctn"},{"clinical-trial-number":"isrctn42984928","registry":"10.18810\/isrctn"}],"author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8473-9045","authenticated-orcid":false,"given":"Fatema G","family":"Dhaif","sequence":"first","affiliation":[{"name":"Warwick Clinical Trials Unit, University of Warwick Warwick Medical School, Coventry, UK"},{"name":"University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nicholas","family":"Parsons","sequence":"additional","affiliation":[{"name":"Warwick Clinical Trials Unit, University of Warwick Warwick Medical School, Coventry, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2992-048X","authenticated-orcid":false,"given":"David R","family":"Ellard","sequence":"additional","affiliation":[{"name":"Warwick Clinical Trials Unit, University of Warwick Warwick Medical School, Coventry, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jeremy","family":"Rodrigues","sequence":"additional","affiliation":[{"name":"Warwick Clinical Trials Unit, University of Warwick Warwick Medical School, Coventry, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4515-8202","authenticated-orcid":false,"given":"Andrew","family":"Metcalfe","sequence":"additional","affiliation":[{"name":"Warwick Clinical Trials Unit, University of Warwick Warwick Medical School, Coventry, UK"},{"name":"University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,3,12]]},"reference":[{"key":"2026062609363340000_16.3.e112478.1","unstructured":"Disparities OfHI . 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