Roberto Seijas, Marta Rius, Orthopedic Surgery, Garcia Cugat Foundation Quiron Hospital Barcelone, Spain Roberto Seijas, Marian Lorente, Oscar Ares, International Uni- versity of Catalunya Jaume Llopis, Department of Statistics, University of Barcelona, Spain José Luis Hernández, Department of Obstetric and Gynaecology, Hospital of the Sea, Barcelona, Spain Andrea Sallent, Vall Hebron Hospital, Barcelone, Spain Oscar Ares, Hospital Clinic Barcelone, Spain Confict-of-interest statement: The author(s) declare(s) that there is no confict of interest regarding the publication of this paper. Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Com- mons 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 and the use is non- commercial. See: http: //creativecommons.org/licenses/by-nc/4.0/ Correspondence to: Roberto Seijas, MD, PhD, Quiron Hospital Barcelona, Pza. Alfonso Comín 5-7, 08035 Barcelone, Spain. Email: roberto6jas@gmail.com Telephone: +34932172252 Fax: +34932381634 Received: February 9, 2017 Revised: April 19, 2017 Accepted: April 21 2017 Published online: June 28, 2017 ABSTRACT AIM: to evaluate if the lack of experience in musculoskeletal ultrasonography generates measuring errors based on patellar tendon measurements. Ultrasound is recognized as an outstanding tool in musculoskeletal pathology diagnosis, despite being physician- dependent in knowledge as much as in experience. METHODS: Six donated knees (ages 58-71 years old) were chosen for the present study. Four observers performed the measurements, which were length, thickness and width of the patellar tendon; an expert in musculoskeletal ultrasonography (gold standard), an obstetric sonographer, an orthopedic surgeon and a third-year medical student. An external participant collected all data and analyzed results. RESULTS: regarding length, an 8% mean decrease with respect to the gold standard’s mean was observed. With respect to the width, the evaluators showed lower measurements with respect to the gold standard, (less than 5% difference) with no constant systematic error, although a trend of a proportional systematic error was observed (0.59). Third, measurements from observers were an 8% higher than the gold standard’s regarding thickness. The evaluator that most approximated measurements to the gold standard performed was the obstetric sonographer. CONCLUSION: The present paper represents an approach to learning systems in musculoskeletal ultrasound and counseling courses to focus on ultrasound technique knowledge rather than anatomical domains. Key words: Musculoskeletal ultrasound; Patellar tendon; Training; Learning systems; Gold standard © 2017 The Author(s). Published by ACT Publishing Group Ltd. All rights reserved. Seijas R, Lorente M, Llopis J, Rius M, Hernández JU, Sallent A, Ares O. Ultrasound Measurements of Patellar Tendon Differences Depending on Previous Training. International Journal of Orthopaedics 2017; 4(3): 744-748 Available from: URL: http: // www.ghrnet.org/index.php/ijo/article/view/1983 INTRODUCTION Ultrasound is recognized as an outstanding tool in musculoskeletal pathology diagnosis, despite being physician-dependent in knowl- TOPIC HIGHLIGHT Ultrasound Measurements of Patellar Tendon Differences Depending on Previous Training Roberto Seijas, Marian Lorente, Jaume Llopis, Marta Rius, José Luis Hernández, Andrea Sallent, Oscar Ares 744 Int. J. of Orth. 2017 June 28; 4(3): 744-748 ISSN 2311-5106 (Print), ISSN 2313-1462 (Online) Online Submissions: http://www.ghrnet.org/index.php/ijo doi:10.17554/j.issn.2311-5106.2017.04.211 International Journal of Orthopaedics