{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,17]],"date-time":"2026-01-17T21:16:38Z","timestamp":1768684598625,"version":"3.49.0"},"reference-count":20,"publisher":"Springer Science and Business Media LLC","issue":"6","license":[{"start":{"date-parts":[[2025,5,2]],"date-time":"2025-05-02T00:00:00Z","timestamp":1746144000000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"},{"start":{"date-parts":[[2025,5,2]],"date-time":"2025-05-02T00:00:00Z","timestamp":1746144000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"}],"funder":[{"DOI":"10.13039\/501100006752","name":"Universidade do Porto","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100006752","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":["link.springer.com"],"crossmark-restriction":false},"short-container-title":["Pediatr Radiol"],"abstract":"<jats:title>Abstract<\/jats:title>\n          <jats:sec>\n            <jats:title>Background<\/jats:title>\n            <jats:p>With increasing ultrasound use, data for the normal amount of joint fluid and synovial appearances are needed.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Objective<\/jats:title>\n            <jats:p>To establish reference values for knee-ultrasound in healthy volunteers by age. To examine the association of joint fluid and synovial appearances with age, sex, and time spent in sports activities.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Materials and methods<\/jats:title>\n            <jats:p>Prospective, cross-sectional, including 3\u201317-year-old volunteers. Examinations were performed by one of two experienced radiologists after meticulous standardisation of the technique. Knees were examined in 30\u00b0 flexion, in extension and during provocation.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Results<\/jats:title>\n            <jats:p>One hundred twenty-seven volunteers (67 females), median age 10.9\u00a0years (percentile 2.5<jats:sup>th<\/jats:sup>-97.5<jats:sup>th<\/jats:sup>: 3.4\u201317.2), were included. With 30\u00b0 knee flexion, the median amount of suprapatellar recess joint fluid (sagittal view) was 0.5\u00a0mm for females and 0.9\u00a0mm for males (<jats:italic>P<\/jats:italic>\u2009=\u20090.014), increasing to 1.9\u00a0mm and 2.4\u00a0mm (<jats:italic>P<\/jats:italic>\u2009=\u20090.031), respectively, during provocation. The amount of fluid during provocation increased with age for both sexes (<jats:italic>P<\/jats:italic>\u2009=\u20090.007 females; <jats:italic>P<\/jats:italic>\u2009=\u20090.012 males) and by time spent in sport-activities (<jats:italic>P<\/jats:italic>\u2009=\u20090.003). Further, there was a positive association between the presence of joint fluid speckles and sport-activities (<jats:italic>P<\/jats:italic>\u2009=\u20090.039). Median double-layered synovium was 1.5\u00a0mm in 3\u20136-year-olds, increasing to 2.1\u00a0mm in 7\u20139-year-olds and 2.0\u00a0mm in 10\u201317-year-olds (<jats:italic>P<\/jats:italic>\u2009=\u20090.024). No synovial Doppler signal was seen. Observers\u2019 agreement was excellent, with ICC values\u2009\u2265\u20090.9.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Conclusion<\/jats:title>\n            <jats:p>The majority of healthy children have measurable knee joint fluid, more so when examined with a flexed knee and under provocation. Speckles within the joint fluid are seen in one-fourth, especially in males, and the presence of speckles and joint fluid amount are associated with sports-activity.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Graphical Abstract<\/jats:title>\n          <\/jats:sec>","DOI":"10.1007\/s00247-025-06243-0","type":"journal-article","created":{"date-parts":[[2025,5,2]],"date-time":"2025-05-02T13:53:32Z","timestamp":1746194012000},"page":"1127-1137","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Knee-ultrasound: reference values for the amount of joint fluid and synovial appearances in healthy children and adolescents"],"prefix":"10.1007","volume":"55","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0862-6967","authenticated-orcid":false,"given":"S\u00edlvia Costa","family":"Dias","sequence":"first","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7637-9756","authenticated-orcid":false,"given":"Diogo Costa","family":"Carvalho","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2956-4232","authenticated-orcid":false,"given":"Miguel","family":"Castro","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9356-3272","authenticated-orcid":false,"given":"Cl\u00e1udia Camila","family":"Dias","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5007-3000","authenticated-orcid":false,"given":"Isabel","family":"Ramos","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9821-6405","authenticated-orcid":false,"given":"Iva","family":"Brito","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0135-2169","authenticated-orcid":false,"given":"Karen","family":"Rosendahl","sequence":"additional","affiliation":[]}],"member":"297","published-online":{"date-parts":[[2025,5,2]]},"reference":[{"key":"6243_CR1","doi-asserted-by":"publisher","first-page":"767","DOI":"10.1016\/S0140-6736(07)60363-8","volume":"369","author":"A Ravelli","year":"2007","unstructured":"Ravelli A, Martini A (2007) Juvenile idiopathic arthritis. 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