tendon

A tendon is the tough cord of connective tissue that ties a muscle to a bone. Muscles pull rather than push, so a muscle has to be anchored: the tendon carries the pull from the muscle's end across to the bone it moves, and the bone turns at the joint. That is why a muscle's origin and insertion can be named by the bones the tendons reach. The tendon's partner is the ligament, which ties bone to bone at a joint rather than muscle to bone, and swapping them is one of the sharpest pairs the exam keeps: a ligament holds a joint together, a tendon pulls a bone. The knee makes the contrast concrete — the patella, the kneecap, sits inside the tendon of the quadriceps, and the joint is held by ligaments. A tendon carries no signal and contracts nothing of its own.