Patterns of movement-evoked pain during tendon loading and stretching tasks in Achilles tendinopathy: A secondary analysis of a randomized controlled trial

Background: This study aimed to characterize movement-evoked pain during tendon loading and stretching tasks in individuals with Achilles tendinopathy, and to examine the association between movement-evoked pain with the Achilles tendinopathy type (insertional and midportion), biomechanical, and psychological variables.Methods: In this laboratory-based, cross-sectional study, 37 individuals with chronic Achilles tendinopathy participated. Movement-evoked pain intensity (Numeric Rating Scale: 0 to 10) and sagittal-plane ankle biomechanics were collected simultaneously during standing, fast walking, single-leg heel raises, and weight-bearing calf stretch. Description of symptoms, including location of Achilles tendon pain and duration of tendon morning stiffness, as well as pain-related psychological measures, including the Tampa Scale of Kinesiophobia were collected. Linear mixed effects models were built around two paradigms of movement-evoked pain (tendon loading and stretching tasks) with each model anchored with pain at rest.Findings: Movement-evoked pain intensity increased as task demand increased in both models. Lower peak dorsiflexion with walking (13 =-0.187, 95% CI:-0.305,-0.069), higher fear of movement (13 = 0.082, 95% CI: 0.018, 0.145), and longer duration of tendon morning stiffness (13 = 0.183, 95% CI: 0.07, 0.296) were associated with greater pain across tendon loading tasks (R2 = 0.47). Lower peak dorsiflexion with walking (13 =-0.27, 95% CI:-0.41,-0.14), higher dorsiflexion with the calf stretch (13 = 0.095, 95% CI: 0.02, 0.16), and insertional Achilles tendinopathy (13 =-0.93, 95% CI:-1.65,-0.21) were associated with higher pain across tendon stretching tasks (R2 = 0.53).Interpretation: In addition to exercise, the ideal management of Achilles tendinopathy may require adjunct treatments to address the multifactorial aspects of movement-evoked pain.