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Although occupationally induced PIS has been previously reported, the symptoms here were linked to repetitive lifting tasks requiring prolonged extension of the first metacarpophalangeal joint with a wide grip. Dynamic ultrasound showed radial displacement of second compartment tendons by the EPB during aggravating movement, suggesting a novel friction- and stress-driven pathomechanism.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/dynamic-ultrasound-imaging-of-extensor-pollicis-brevis-hypertrophy-in-proximal-intersection-syndrome-a-case-report-and-literature-review/439294/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/dynamic-ultrasound-imaging-of-extensor-pollicis-brevis-hypertrophy-in-proximal-intersection-syndrome-a-case-report-and-literature-review/439294.png","ImageObject",300,407,{"name":92,"@type":93},"Aria Callaghan","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-01","2026-09-29",true,{"@type":102,"interactionType":103,"userInteractionCount":14},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What diagnosis is addressed in this case report?","Question",{"text":112,"@type":113},"The report focuses on proximal intersection syndrome (PIS), specifically an atypical form associated with extensor pollicis brevis hypertrophy and edema identified by ultrasound.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How was the aggravating movement evaluated?",{"text":117,"@type":113},"Dynamic ultrasound assessment was performed during the movement that worsened symptoms, demonstrating radial displacement of second compartment tendons by the extensor pollicis brevis muscle.",{"name":119,"@type":110,"acceptedAnswer":120},"What activity was linked to the patient’s symptoms?",{"text":121,"@type":113},"Symptoms were associated with repetitive lifting tasks, including overhead reaching on tiptoes and lifting/lowering a weighted basket with a wide hand grip.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},439294,1790815195,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":14,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":34,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":143,"read_time":144},962084926284,"https://ap-avatar.wpscdn.com/davatar_29158cc5080c5b710cf443261637dec0","Journal of Clinical Ultrasound  \nCASE REPORT  OPEN ACCESS   \nDynamic Ultrasound Imaging of Extensor Pollicis Brevis Hypertrophy in Proximal Intersection Syndrome: A Case Report and Literature Review  \nDaoukas Stavros1,2  | Galanis Dimitrios3 | Mathew Benoy4 | Malliaropoulos Nikos5,6  \n1College of Health and Life Sciences, London South Bank University, London, UK | 2Radiology Department, Queen's Hospital NHS Trust, Barking, Havering and Redbridge University Hospital (BHRUT), London, UK | 312th Orthopaedic Department, Metropolitan General Hospital, Athens, Greece | 4Guys and St. Thomas Hospital, London, UK | 5Centre for Sports and Exercise Medicine, William Harvey Research Institute, Queen Mary  \nUniversity London, London, UK | 6Rheumatology Department, Mile End Hospital, Barts Health NHS Trust, London, UK Correspondence: Daoukas Stavros ([daoukass@lsbu.ac.uk](daoukass@lsbu.ac.uk))  \nReceived: 25 March 2025 | Revised: 18 May 2025 | Accepted: 11 July 2025  \nKeywords: differential diagnosis | overuse syndrome | sonography | tendinopathy | wrist pain  \nABSTRACT  \nThis case report presents an atypical presentation of proximal intersection syndrome and provides ultrasound-based evidence of extensor pollicis brevis muscle belly hypertrophy with associated edema in a non-athletic population. While occupationally induced PIS has been previously documented, the patient's symptoms in this case were linked to repetitive lifting tasks involving prolonged extension of the first metacarpophalangeal joint with a wide grip. Dynamic ultrasound assessment revealed radial displacement of the second compartment tendons by the extensor pollicis brevis muscle during the aggravating movement. This finding suggests a novel pathomechanism, potentially driven by mechanical friction and stress between the first and second dorsal compartments, warranting further investigation.  \n1 | Introduction  \nProximal intersection syndrome (PIS) is characterized by stenosing tenosynovitis at the musculotendinous junctions where the first compartment, comprising the abductor pollicis longus (APL) and extensor pollicis brevis (EPB), intersects with the second compartment, which includes the extensor carpi radialis longus (ECRL), and extensor carpi radialis brevis (ECRB) (Tanet al. 2024; Schmidt et al. 2021; Hoy et al. 2019; Balakatouniset al. 2017) . This condition is typically triggered by repetitive wrist motions, leading to friction and inflammation at these crossover points, predominantly 4–6 cm proximal to the Lister's  \ntubercle. Common signs and symptoms include pain, swelling, erythema, and crepitus along the distal dorsal-radial forearm (Tan et al. 2024; Schmidt et al. 2021; Montechiarello et al. 2010) .  \nThis case report explores an atypical presentation of PIS in anon-athletic individual, where ultrasound findings revealed muscle belly hypertrophy of the EPB and associated edema as potential contributors to the pathology. This report, building on previous occupational presentations of PIS, highlights an alternative pathomechanism based on dynamic sonographic findings and proposes novel risk factors and diagnostic considerations for this condition.  \nThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.  \n© 2025 The Author(s). Journal of Clinical Ultrasound published by Wiley Periodicals LLC.  \nJournal of Clinical Ultrasound, 2026; 54:213–219 213  \n[https://doi.org/10.1002/jcu.70018](https://doi.org/10.1002/jcu.70018)  \nFIGURE 1 | Site of symptoms. The marked area (blue circle) highlights the location of patient-reported radial-sided clicking, crepitus sensations, and pain, approximately 4 cm proximal to the Lister's tubercle on the dorsal aspect of the left forearm.  \nFIGURE 2 | Raised contour at the proximal intersection. The blue arrow highlights the area of mild raised contour, mild swelling, on the dorsal asp","cbCailElB7pCJ0ND","https://ap.wps.com/l/cbCailElB7pCJ0ND","pdf",999501,"English","# Introduction\n# Case Report\n## Patient Presentation\n## Dynamic Ultrasound Findings\n# Discussion\n# Conclusion","[{\"question\":\"What diagnosis is addressed in this case report?\",\"answer\":\"The report focuses on proximal intersection syndrome (PIS), specifically an atypical form associated with extensor pollicis brevis hypertrophy and edema identified by ultrasound.\"},{\"question\":\"How was the aggravating movement evaluated?\",\"answer\":\"Dynamic ultrasound assessment was performed during the movement that worsened symptoms, demonstrating radial displacement of second compartment tendons by the extensor pollicis brevis muscle.\"},{\"question\":\"What activity was linked to the patient’s symptoms?\",\"answer\":\"Symptoms were associated with repetitive lifting tasks, including overhead reaching on tiptoes and lifting/lowering a weighted basket with a wide hand grip.\"}]","Dynamic Ultrasound Imaging of Extensor Pollicis Brevis Hypertrophy in Proximal Intersection Syndrome - A Case Report and Literature Review | PDF",1790688077,18]