Exploring biomarkers of change in movement-evoked pain in Achilles tendinopathy: A secondary analysis of a randomized controlled trial.

BACKGROUND

Movement-evoked pain contributes to disability, yet factors that predict improvement in pain with rehabilitation remain largely unknown. We aimed to identify predictors and response biomarkers of the reduction in movement-evoked pain intensity with rehabilitation in individuals with Achilles tendinopathy (AT).

METHODS

Individuals with AT (n = 65) were evaluated at baseline and after 8-weeks of rehabilitation. Pain (Numeric Rating Scale, 0 to 10) was collected during increasingly difficult tendon-loading (resting, walking, heel raises) and stretching (resting, standing, calf stretch) tasks. Psychological, ankle biomechanics, and clinical variables were collected. Linear mixed effects models were built around two paradigms of pain (tendon loading and stretching tasks) to determine variables predictive of change in pain (predictive biomarkers) and variables that changed along with change in pain (response biomarkers) with rehabilitation.

FINDINGS: Lower ankle dorsiflexion during walking (β = 0.178, 95 %CI:0.06, 0.29), higher ankle dorsiflexion during stretching (β = -0.111, 95 %CI:-0.174, -0.05), a lower Victorian Institute of Sports Assessment- Achilles (VISA-A) score (β = 0.031, 95 % CI:0.010, 0.054), and younger age (β = 0.047, 95 %CI:0.022, 0.072) at baseline predicted a greater reduction in pain. For response biomarkers, reductions in duration of tendon stiffness (β = 0.018, 95 %CI: 0.001, 0.036), increases in ankle dorsiflexion during walking (β = -0.15, 95 %CI:-0.285, -0.016), reductions in depression (β = 0.109, 95 % CI:0.041, 0.178), and reductions in kinesiophobia (β = 0.151, 95 %CI:0.083, 0.219) were associated with greater reductions in pain. AT type was not associated with pain.

INTERPRETATION: Regardless of AT type, kinesiophobia, ankle dorsiflexion, and clinical factors may be important factors to consider as predictors and/or response indicators for reductions in movement-evoked pain with rehabilitation.

STUDY REGISTRATION: https://clinicaltrials.gov/study/NCT04059146.