A tendon was a tough band of fibrous connective tissue that usually connected muscle to bone, capable of withstanding tension.
In 2373, after having sex with Grilka, Quark was left with strained tendons, along with several other injuries. (DS9: "Looking for par'Mach in All the Wrong Places")
Also that year, Marayna pulled a tendon in her leg and placed Harry Kim's hand upon it, much to his embarrassment. (VOY: "Alter Ego")