{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T14:27:34Z","timestamp":1777386454452,"version":"3.51.4"},"reference-count":14,"publisher":"SAGE Publications","issue":"6","license":[{"start":{"date-parts":[[1989,11,1]],"date-time":"1989-11-01T00:00:00Z","timestamp":625881600000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.sagepub.com\/page\/policies\/text-and-data-mining-license"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Am J Sports Med"],"published-print":{"date-parts":[[1989,11]]},"abstract":"<jats:p>The knee extensor mechanism was examined in 32 male competitive volleyball players (Group V) and in a control group of 49 young adult males (Group C) to evaluate the effects of previous jumping activity on the knee extensor mechanism. Several variables were re corded by means of a structured questionnaire, and by clinical and radiographic examination.<\/jats:p>\n                  <jats:p>The amount of physical activity from the age of 7 years onward was significantly greater in Group V than in Group C. The incidence of anterior knee pain during the year preceding the examination was higher in Group V (31%) than in Group C (6%;P &lt; 0.01). The most common reason for anterior knee pain in Group V was so-called \"jumper's knee.\" No significant difference be tween the groups was found in the incidence of clinical symptoms and signs of patellar chondromalacia. There were radiologically detectable soft tissue calcifications at the upper or lower pole of the patella or anterior to the patella in 38% of the subjects in Group V, but no such calcifications were seen in Group C ( P &lt; 0.001). However, persistent symptoms did not correlate with the calcifications. Group V subjects had a slight but significant trend to patella alta when compared to Group C ( P &lt; 0.05) according to the Blackburne and Peel index.<\/jats:p>","DOI":"10.1177\/036354658901700607","type":"journal-article","created":{"date-parts":[[2007,6,21]],"date-time":"2007-06-21T20:46:52Z","timestamp":1182458812000},"page":"766-769","source":"Crossref","is-referenced-by-count":24,"title":["The effect of volleyball playing on the knee extensor mechanism"],"prefix":"10.1177","volume":"17","author":[{"given":"U.M.","family":"Kujala","sequence":"first","affiliation":[{"name":"Paavo Nurmi Center, Sports Medical Research Unit, Turku, Finland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"T.","family":"Aalto","sequence":"additional","affiliation":[{"name":"Rehabilitation Research Center of the Social Insurance Institution, Turku, Finland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"K.","family":"\u00d6sterman","sequence":"additional","affiliation":[{"name":"Orthopaedic Hospital of the Invalid Foundation, Helsinki, Finland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"S.","family":"Dahlstrom","sequence":"additional","affiliation":[{"name":"Central Military Hospital, Helsinki, Finland"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"179","published-online":{"date-parts":[[1989,11,1]]},"reference":[{"key":"atypb1","doi-asserted-by":"crossref","unstructured":"Blackburne JS , Peel TE A new method of measuring patellar height . 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An experimental study of the effects of growth on the relationship of tendons and ligament to bone at the site of diaphyseal insertion Ann Chir Gynaec Fenn (Suppl) 59: 35-41, 1970","DOI":"10.3109\/ort.1970.41.suppl-131.01"}],"container-title":["The American Journal of Sports Medicine"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/journals.sagepub.com\/doi\/pdf\/10.1177\/036354658901700607","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.sagepub.com\/doi\/pdf\/10.1177\/036354658901700607","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T09:36:11Z","timestamp":1777368971000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.sagepub.com\/doi\/10.1177\/036354658901700607"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1989,11]]},"references-count":14,"journal-issue":{"issue":"6","published-print":{"date-parts":[[1989,11]]}},"alternative-id":["10.1177\/036354658901700607"],"URL":"https:\/\/doi.org\/10.1177\/036354658901700607","relation":{},"ISSN":["0363-5465","1552-3365"],"issn-type":[{"value":"0363-5465","type":"print"},{"value":"1552-3365","type":"electronic"}],"subject":[],"published":{"date-parts":[[1989,11]]}}}