Heterogeneity of passive elastic properties within the quadriceps femoris muscle–tendon unit

Purpose The purpose of this study was to compare regional elastic properties between anterior and posterior regions of the patellar tendon, and individual quadriceps muscles, over a range of knee flexion angles. Methods An isokinetic dynamometer passively positioned the non-dominant knee of 19 young, healthy participants, at 25°, 40°, 55°, 70° and 85° flexion. Shear wave velocity (SWV, an index of tissue elasticity) was measured using ultrasound shear wave elastography in a relaxed (passive) state, confirmed by electromyography. Results SWV of the patellar tendon and quadriceps muscles increased with knee flexion (longer muscle–tendon unit; P