Background: The aims of this study were to clarify the changes of patellar tendon length during isometric knee joint extension and the double leg squat position using ultrasonography. Methods: The left legs of 17 healthy adults were investigated. Isometric knee extension motion was performed at three positions of knee flexion 30° (knee 30°), knee flexion 60° (knee 60°), knee flexion 90° (knee 90°), and at each limb position, 0% (0% peak torque (PT)), 40% (40% PT), 50% (50% PT), and 60% (60% PT) of the maximum knee joint extension torque were executed at random. Both double leg squat motions were randomly performed in three positions: hip flexion 30°, knee flexion 30°, ankle dorsiflexion 10° (squat 30°); hip joint flexion 60°, knee joint flexion 60°, ankle dorsiflexion 20° (squat 60°); and hip joint flexion 90°, knee joint flexion 90°, ankle dorsiflexion 30° (squat 90°). Ultrasonography was used to measure patellar tendon length. Findings: There were no significant changes in patellar tendon length and strain between knee flexion angles of 30°, 60°, and 90° in isometric knee joint extension and the double leg squat limb position. Interpretation: The loading rate and limb position do not appear to affect the length and strain of the patellar tendon.
Edama, M., Okuyama, R., Goto, S., & Sasaki, M. (2019). Influence of loading rate and limb position on patellar tendon mechanical properties in vivo. Clinical Biomechanics, 61, 52–57. https://doi.org/10.1016/j.clinbiomech.2018.11.006