title: Central pain processing is altered in people with Achilles tendinopathy.
abstract: BACKGROUND
  Tendinopathy is often a chronic condition. The mechanisms behind persistent tendon pain are not yet fully understood. It is unknown whether, similar to other persistent pain states, central pain mechanisms contribute to ongoing tendon pain.
  
  
  OBJECTIVE
  We investigated the presence of altered central pain processing in Achilles tendinopathy by assessing the conditioned pain modulation (CPM) effect in people with and without Achilles tendinopathy.
  
  
  METHODS
  20 people with Achilles tendinopathy and 23 healthy volunteers participated in this cross-sectional study. CPM was assessed by the cold pressor test. The pressure pain threshold (PPT) was recorded over the Achilles tendon before and during immersion of the participant's hand into cold water. The CPM effect was quantified as the absolute difference in PPT before and during the cold pressor test.
  
  
  RESULTS
  An increase in PPT was observed in the Achilles tendinopathy and control group during the cold pressor test (p<0.001). However, the CPM effect was stronger in the control group (mean difference=160.5 kPa, SD=84.9 kPa) compared to the Achilles tendinopathy group (mean difference=36.4 kPa, SD=68.1 kPa; p<0.001).
  
  
  CONCLUSIONS
  We report a reduced conditioned pain modulation effect in people with Achilles tendinopathy compared to people without Achilles tendinopathy. A reduced conditioned pain modulation effect reflects altered central pain processing which is believed to contribute to the persistence of pain in other conditions. Altered central pain processing may also be an important factor in persistent tendon pain that has traditionally been regarded to be dominated by peripheral mechanisms.
authors.affiliation: Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, MOVE Research Institute Amsterdam, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Nefeli
authors.initials: N
authors.lastname: Tompra
authors.affiliation: Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, MOVE Research Institute Amsterdam, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Jaap H
authors.identifier: http://orcid.org/0000-0002-7719-5585
authors.initials: JH
authors.lastname: van Dieën
authors.affiliation: Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, MOVE Research Institute Amsterdam, VU University Amsterdam, Amsterdam, The Netherlands Department of Physiotherapy, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Michel W
authors.initials: MW
authors.lastname: Coppieters
mesh_terms: D000125:Achilles Tendon / Q000502:physiology*; D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D059333:Central Nervous System Sensitization / Q000502:physiology; D059350:Chronic Pain / Q000503:physiopathology*; D003080:Cold Temperature; D006801:Humans; D059226:Nociceptive Pain / Q000503:physiopathology; D010147:Pain Measurement; D058748:Pain Perception / Q000502:physiology*; D052256:Tendinopathy / Q000503:physiopathology*
keywords: Achilles tendon; Assessment; Tendinopathy