Influence of loading rate and limb position on patellar tendon mechanical properties in vivo.

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.