Tendon loading in runners with Achilles tendinopathy: Relations to pain, structure, and function during return-to-sport

Abstract

We aimed to (1) compare pain, tendon structure, lower limb function, and Achilles tendon loads while running between limbs in runners with Achilles tendinopathy, and (2) explore the relations of pain, tendon structure, and lower limb function to Achilles tendon loads while running. Twenty runners with Achilles tendinopathy participated in this pilot study. Pain was assessed with questionnaires, quantitative sensory testing, and functional testing. Tendon morphology and mechanical properties were evaluated with ultrasound imaging, continuous shear wave elastography, and ultrasound imaging combined with dynamometry. Lower limb function was assessed with an established test battery. Achilles tendon loads were estimated from biomechanical data acquired during running. Compared to the least symptomatic limb, the most symptomatic limb had lower scores on the Victorian Institute of Sports Assessment - Achilles questionnaire and worse pain during drop countermovement jumping, hopping, and running. Tendon thickness and cross-sectional area were greater, and Young's modulus, drop countermovement jump height, and plyometric quotient during hopping were lower on the most symptomatic limb. Side-to-side differences in drop countermovement jump height were significantly associated with side-to-side differences in Achilles tendon peak forces and average loading rates during running. Various measures of pain, structure, and function differ between limbs in runners with Achilles tendinopathy during return-to-sport. Tendon forces, however, do not differ between limbs during comfortable running. In addition to measures that differ between limbs, measures of performance during drop countermovement jumping may aid in clinical decision-making during return-to-sport because they are associated with tendon forces while running.

Keywords: biomechanics; mechanical properties; physical performance; running; tendinitis; ultrasonography.

FIGURE 1

Pressure-pain threshold testing of the Achilles tendon with a mechanical algometer (Somedic SenseLab AB, Sösdala, Sweden)

FIGURE 2

Ultrasound images revealing position of medial gastrocnemius (MG) myotendinous junction at rest (1) and during ankle plantar flexion maximal voluntary isometric contraction (2). Line A was drawn parallel to the right edge of the rubber tape shadow. The change in Line B was used to adjust for movement of the ultrasound transducer. The change in Line C was used to measure linear displacement of the medial gastrocnemius myotendinous junction along the long-axis of the lower leg

FIGURE 3

Average Achilles tendon forces during comfortable treadmill running for the most (black solid line) and least (gray solid line) symptomatic limbs of individuals with Achilles tendinopathy during the return-to-sport phase. Dashed lines represent ±1 standard deviation