The Achilles tendon is the most powerful tendon in the human body. Tendons are strong tissues that connect muscles to bone. The Achilles tendon is located in the lower back part of the leg and works with the calf muscles to provide forceful foot movements. Achilles tendon ruptures most commonly occur as a result of sports injuries from activities such as basketball, football, or tennis. They can also result from a condition called Achilles tendonitis. Individuals with Achilles tendonitis have weakened and inflamed tendons that are susceptible to injury.