The state of tissue hydration determines the strain-rate-sensitive stiffness of human patellar tendon.

The purpose of this study was to investigate the effect of tissue hydration on the structural properties of human patellar tendon. Specimens were subjected to a load relaxation experiment prior to being stretched to failure. The experiments indicated that tendons relaxed faster in hypotonic solutions when compared to hypertonic solutions. At a strain rate of 50% s-1 the structural stiffness was significantly higher while immersed in a hypotonic versus hypertonic solution. No difference in tensile stiffness was documented between baths for 0.5% s-1. Tendons immersed in the hypotonic solution were significantly stiffer for 50% s-1 against 0.5% s-1. The results indicate that the structural properties of human patellar tendon are more sensitive to time when the tissues are fully hydrated.