title: Altered tendon characteristics and mechanical properties associated with insertional achilles tendinopathy.
abstract: METHODS
  Case-control laboratory study.
  
  
  OBJECTIVE
  To compare tendon characteristics (shape, composition) and mechanical properties (strain, stiffness) on the involved side of participants with insertional Achilles tendinopathy (IAT) to the uninvolved side and to controls, and to examine if severity of tendon pathology is associated with severity of symptoms during function.
  
  
  BACKGROUND
  Despite the severity and chronicity of IAT, the quality of theoretical evidence available to guide the development of exercise interventions is low. While tendon pathology of midportion Achilles tendinopathy has been described, there are few studies specific to IAT.
  
  
  METHODS
  Twenty individuals with unilateral IAT and 20 age- and sex-matched controls volunteered to participate. Ultrasound imaging was used to quantify changes in tendon shape (diameter) and composition (echogenicity). A combination of ultrasound and dynamometry was used to measure tendon mechanical properties (strain and stiffness) during passive ankle rotation toward dorsiflexion. Generalized estimating equations were used to examine the association between IAT, alterations in tendon properties, and participant demographics. Pearson correlation was used to examine the association between severity of tendon pathology and severity of symptoms (Victorian Institute of Sport Assessment-Achilles).
  
  
  RESULTS
  The side with IAT had a larger tendon diameter (P<.001), lower echogenicity (P<.001), higher strain (P = .011), and lower stiffness (P = .007) compared to the side without IAT and the controls. On the involved side of participants with IAT, a lower echogenicity correlated with higher severity of symptoms (r = 0.603, P = .010).
  
  
  CONCLUSIONS
  Ultrasound imaging combined with dynamometry can discriminate alterations in tendon shape, composition, and mechanics in participants with IAT. Future clinical trials for IAT may consider strategies to alter tendon characteristics and restore tendon mechanics.
authors.affiliation: Department of Biomedical Engineering, University of Rochester Medical Center, Rochester, NY.
authors.forename: Ruth L
authors.initials: RL
authors.lastname: Chimenti
authors.forename: Adolph S
authors.initials: AS
authors.lastname: Flemister
authors.forename: Joshua
authors.initials: J
authors.lastname: Tome
authors.forename: James M
authors.initials: JM
authors.lastname: McMahon
authors.forename: Marie A
authors.initials: MA
authors.lastname: Flannery
authors.forename: Ying
authors.initials: Y
authors.lastname: Xue
authors.forename: Jeff R
authors.initials: JR
authors.lastname: Houck
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D052256:Tendinopathy / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology*; D014463:Ultrasonography
keywords: ankle; plantar flexors; tendon; triceps surae; ultrasound