{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,18]],"date-time":"2025-11-18T12:29:39Z","timestamp":1763468979352,"version":"3.40.5"},"reference-count":47,"publisher":"Public Library of Science (PLoS)","issue":"10","license":[{"start":{"date-parts":[[2024,10,21]],"date-time":"2024-10-21T00:00:00Z","timestamp":1729468800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS ONE"],"abstract":"<jats:p>Osteoarthritis (OA) knee is one of the most common chronic degenerative conditions that imposes clinical and economic burdens on individuals and societies worldwide. Previous studies showed vitamin D levels correlated positively with lean muscle mass and grip strength, implying that vitamin D supplementation may improve muscle health in knee OA subjects. This randomized controlled trial (RCT) aims to compare the effects of vitamin D supplementation on knee muscle strength, physical function, pain, and sarcopenia status in patients with end-stage knee OA. Patients and outcome assessors will be blinded to group allocation. Fifty-six end-stage knee OA patients with vitamin D insufficiency fulfilling our inclusion criteria will be invited to participate in this study. Patients will be randomly assigned to take vitamin D supplementation (4,000 IU capsule daily) or placebo for six months. Measurements will be taken at baseline, three and six-month after the commencement of the vitamin D supplement, and 6-month after the interventional period. The primary outcome includes the isometric quadriceps and hamstring muscle strength measured by a hand-held dynamometer. Secondary outcomes include pain, performance-based and self-reported physical function and sarcopenia status. The success of this study will provide scientific evidence of whether the relatively cheap and well-tolerated vitamin D supplement can improve quadriceps muscle strength, physical function, pain symptoms, and sarcopenia status of this increasingly large population for end-stage knee OA patients. The study has great clinical significance given Hong Kong\u2019s lengthy and growing waiting list for complete knee replacement procedures.<\/jats:p>\n<jats:p><jats:bold>Trial registration:<\/jats:bold> The trial was registered on clinicaltrials.gov (<jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"uri\" xlink:href=\"https:\/\/clinicaltrials.gov\/study\/NCT05981534\" xlink:type=\"simple\">NCT05981534<\/jats:ext-link>) on 31<jats:sup>st<\/jats:sup> July 2023.<\/jats:p>","DOI":"10.1371\/journal.pone.0309610","type":"journal-article","created":{"date-parts":[[2024,10,21]],"date-time":"2024-10-21T17:27:34Z","timestamp":1729531654000},"page":"e0309610","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":1,"title":["The effectiveness of vitamin D supplementation in patients with end-stage knee osteoarthritis: Study protocol for a double-blinded, randomized controlled trial"],"prefix":"10.1371","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-3700-7611","authenticated-orcid":true,"given":"Qian-Wen","family":"Wang","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4460-9286","authenticated-orcid":true,"given":"Michael Tim-Yun","family":"Ong","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Gene Chi-Wai","family":"Man","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yi-Man","family":"Yeung","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xin","family":"He","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ben Chi-Yin","family":"Choi","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jonathan Patrick","family":"Ng","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Daniel Kam-Wah","family":"Mok","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2427-2719","authenticated-orcid":true,"given":"Tsz-Ping","family":"Lam","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Patrick Shu-Hang","family":"Yung","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"340","published-online":{"date-parts":[[2024,10,21]]},"reference":[{"key":"pone.0309610.ref001","doi-asserted-by":"crossref","first-page":"26","DOI":"10.1002\/art.23176","article-title":"Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. 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