1) Achilles tendonitis is inflammation of the Achilles tendon in the back of the ankle with symptoms of pain when walking, pushing off, or jumping. 2) An Achilles rupture is a complete or partial tear of the Achilles tendon that causes a loud pop and inability to stand on toes. 3) Treatment for tendonitis is rest, ice, and physical therapy while a rupture requires immobilization and possibly surgery followed by a lengthy rehabilitation process.