Achilles tendonitis: Inflammation in the tendon of the calf muscle, where it attaches to the heel bone. Achilles tendonitis causes pain and stiffness at the back of the leg, near the heel. Achilles tendonitis can be caused by overuse of the Achilles tendon, overly tight calf muscles or Achilles tendons, excess uphill running, a sudden increase in the intensity of training or the type of shoes worn to run, or wearing high heels at work and then switching to a lower-heeled workout shoe. Achilles tendonitis causes pain, tenderness, and often swelling over the Achilles tendon. There is pain on rising up on the toes and pain with stretching of the tendon. The range of motion of the ankle may be limited. Treatment includes applying ice packs to the Achilles tendon, raising the lower leg, and taking an anti-inflammatory medication. In some severe cases of Achilles tendonitis, a cast may be needed for several weeks. A heel lift insert may also be used in shoes to prevent future overstretching of the Achilles tendon. Exerting rapid stress on the Achilles tendon when it is inflamed can result in rupture of the tendon.