A tendon is a flexible band of fibrous tissue. The tendon is the structure in our body that connects your muscles to the bones. The skeletal muscles in your body are responsible for moving your bones, thus enabling you to walk, jump, lift, and move in many ways. When a muscle contracts it pulls on a bone to cause movements. The structure that transmits the force of the muscle contraction to the bone is called a tendon.
Tendons come in many shapes and sizes. Some are very small, like the ones that cause movements of your fingers, and some are much larger, such as your Achilles tendon in your heel. When functioning normally, these tendons glide easily and smoothly as the muscle contracts.
Sometimes the tendons become inflamed for a variety of reasons, and the action of pulling the muscle becomes irritating. If the normal smooth gliding motion of your tendon is impaired, the tendon will become inflamed and movement will become painful. This is called tendonitis, and literally means inflammation of the tendon.