February 2019

Transverse tendon stiffness is reduced in people with Achilles tendinopathy: A cross-sectional study

Evan Finnamore, Charlotte Waugh, Lyndal Solomons, Michael Ryan, Christopher West, Alexander Scott
Centre for Hip Health and Mobility, Vancouver Coastal Health Research Institute, Vancouver, Canada, Department of Physical Therapy, Faculty of Medicine, University of British Columbia, Vancouver, Canada; Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada; Southern Medical Program, Department of Cellular and Physiological Sciences, University of British Columbia (Okanagan), Kelowna, Canada
PLOS ONE - February 20th, 2019 (DOI: 10.1371/journal.pone.0211863)

Objectives: The objective of the current cross-sectional study was to examine Achilles tendon transverse stiffness in a group of recreational runners with Achilles tendinopathy, in comparison to an asymptomatic group of runners with similar training history. We also aimed to determine the between-week intra-individual reliability of this measurement technique.

Study design: Cross-sectional cohort study.

Methods: A hand-held dynamometer was used to assess the transverse stiffness of the Achilles tendon (AT) in twenty-five recreational runners. In ten people with midportion Achilles tendinopathy (5 men, 5 women), measurements were taken directly over the most symptomatic location. In 15 people who were free of AT symptoms (7 men, 8 women), measurements were taken at an equivalent location on the tendon. Participants returned after one week to determine measurement reliability (intra-class correlation coefficient/ICC and minimum detectable change/MDC95). We also collected information about people’s tendon loading activities, tendon thickness (ultrasound mesaurement), and symptoms (Victorian Institute of Sports Assessment–Achilles / VISA-A score).

Results: The AT transverse stiffness was lower in people with Achilles tendinopathy (777 N/m ± 86) compared to those who were asymptomatic (873 N/m ± 72) (p < 0.05). AT transverse stiffness was negatively correlated with age and tendon thickness, and positively correlated with VISA-A score and waist circumference. Reliability was good, with ICC of 0.81 in people with tendinopathy and 0.80 in healthy controls, and an MDC95 of 118 and 87N/m in these two respective groups.

Transverse Achilles tendon stiffness can be reliably measured in people with midportion Achilles tendinopathy, and appears to be lower in people who are older, more symptomatic, and with more extensive tendon thickening. The potential clinical utility of monitoring tendon stiffness in the management of tendon injuries merits further study.