title: Structural integrity is decreased in both Achilles tendons in people with unilateral Achilles tendinopathy.
abstract: OBJECTIVE
  A high proportion of Achilles tendinopathy patients develop bilateral symptoms with human and animal studies showing bilateral histological changes associated with overuse/pathology in one tendon. The current study examined changes in tendon structure, assessed semi-quantitatively using ultrasound tissue characterisation, in both the symptomatic and asymptomatic tendon in unilateral Achilles tendinopathy patients in comparison to individuals with no history of tendinopathy.
  
  
  METHODS
  Cross-sectional case-control study.
  
  
  METHODS
  Participants with Achilles tendinopathy (n=21), with varying severity and length of clinical symptoms, and six participants with no history of tendinopathy were recruited. Tendons were scanned using ultrasound tissue characterisation, which captures contiguous transverse ultrasound images every 0.2mm and renders a 3-dimensional image. Ultrasound tissue characterisation quantifies tendon structure by measuring the stability of echopattern over contiguous transverse images. Four echo-types were discriminated and expressed as a percentage. Antero-posterior diameter of all tendons was measured.
  
  
  RESULTS
  Significant differences were observed in the proportion of normal tendon structure between all three groups (p<0.01), with the symptomatic tendon containing the least amount of normal tendon structure (symptomatic - 79.5%, asymptomatic - 81.8%, control - 86.4%). The asymptomatic tendon contained significantly less normal tendon in comparison to the control tendon (p=0.008), suggesting the asymptomatic tendon is structurally compromised despite the absence of symptoms.
  
  
  CONCLUSIONS
  Both Achilles tendons are structurally compromised in patients with unilateral Achilles tendinopathy. Future studies need to investigate whether these changes increase the risk of developing symptoms.
authors.affiliation: School of Primary Health Care, Monash University, Australia; Carlton Football Club, Australia. Electronic address: sean.docking@monash.edu.
authors.forename: Sean I
authors.initials: SI
authors.lastname: Docking
authors.affiliation: Carlton Football Club, Australia; Centre for Health, Exercise and Sports Medicine, University of Melbourne, Australia.
authors.forename: Samuel D
authors.initials: SD
authors.lastname: Rosengarten
authors.affiliation: St Vincents Hospital, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Daffy
authors.affiliation: School of Primary Health Care, Monash University, Australia.
authors.forename: Jill
authors.initials: J
authors.lastname: Cook
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging* / Q000473:pathology; D000328:Adult; D058070:Asymptomatic Diseases; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D052256:Tendinopathy / Q000000981:diagnostic imaging* / Q000473:pathology; D014463:Ultrasonography; D055815:Young Adult
keywords: Achilles tendon; Bilateral; Tendinopathy; UTC; Ultrasonography