Patients with insertional achilles tendinopathy exhibit differences in ankle biomechanics as opposed to strength and range of motion

Abstract

STUDY DESIGN: Controlled laboratory study; cross-sectional. BACKGROUND: Little is known about ankle range of motion (ROM) and strength among patients with insertional Achilles tendinopathy (IAT) and whether limited ankle ROM and plantar flexor weakness impact IAT symptom severity. OBJECTIVES: The purposes of the study were (1) to examine whether participants with IAT exhibit limited non-weight-bearing dorsiflexion ROM, reduced plantar flexor strength, and/or altered ankle biomechanics during stair ascent; and (2) to determine which impairments are associated with symptom severity. METHODS: Participants included 20 patients with unilateral IAT (mean ± SD age, 59 ± 8 years; 55% female) and 20 individuals without tendinopathy (age, 58.2 ± 8.5 years; 55% female). A dynamometer was used to measure non-weightbearing ROM and isometric plantar flexor strength. Three-dimensional motion analysis was used to quantify ankle biomechanics during stair ascent. End-range dorsiflexion was quantified as the percentage of non-weight-bearing dorsiflexion used during stair ascent. Group differences were compared using 2-way and 1-way analyses of variance. Pearson correlations were used to test for associations among dependent variables and symptom severity. RESULTS: Groups differed in ankle biomechanics, but not non-weight-bearing ROM or strength. During stair ascent, the IAT group used greater end-range dorsiflexion (P = .03), less plantar flexion (P = .02), and lower peak ankle plantar flexor power (P = .01) than the control group. Higher end-range dorsiflexion and lower ankle power during stair ascent were associated with greater symptom severity (P