A Case-control Study of Insertional Achilles Tendinopathy Impairments: Tendon Characteristics, Dorsiflexion Range of Motion, and Plantar Flexion Strength

Purpose: The purpose of this study was to test clinical theories on how impairments in tendon characteristics, dorsiflexion (DF) range of motion (ROM) and plantar flexion (PF) strength were related to insertional achilles tendinopathy (IAT). The association between these impairments and function was also examined.;Methods: Twenty individuals with IAT (age= 58.6+/- 7.8 years, 55% female) and 20 age-- and gender-matched controls (age= 58.2+/- 8.5 years, 55% female) volunteered for this study. Tendon characteristics (diameter, echogenicity, strain, stiffness) were measured using a combination of ultrasound imaging and an isokinetic dynamometer. Three dimensional motion analysis was used to quantify ROM and functional strength during clinical tests and stair ascent. Plantar flexion isometric strength was also documented. Sides with IAT (n=20) were compared to sides without IAT (n=60) using Generalized Estimating Equations (GEE). The correlations between impairments and self-reported function (assessed using the Victorian Institute Sports Assessment- Achilles questionnaire) were also examined.;Results: Sides with IAT had a larger tendon diameter (P<0.001), lower echogenicity (P<0.001), higher strain ( P=0.007) and lower stiffness (P=0.001) than sides without IAT. There was not evidence of differences between groups in clinical tests of DF (P=0.414), but there were significant differences in the percent of available DF used during stair ascent ( P=0.042). Sides with IAT had lower isometric PF strength than sides without IAT (P=0.010) and used lower ankle power ( P<0.001) during stair ascent than sides without IAT. Impairments in echogenicity, and functional use of DF and PF strength were associated with lower function (P<0.05).;Conclusions: Clinical theories associating tendon degeneration with IAT were supported by the alterations in tendon ultrasound imaging. Further, the impingement theory of IAT tendinopathy was supported. Tendon pathology, defined using ultrasound imaging, and impairments influence functional status in persons with IAT.;Clinical implications: Although prospective research is needed, ultrasound imaging is promising as a clinical marker of IAT severity. Evaluation of DF ROM and PF strength are important because of their link to function. However, because decreased DF ROM is not typically associated with IAT and IAT tendons show increased stiffness, routine stretching may be overprescribed and strengthening overlooked.