The Achilles tendon is the largest tendon in the body. It connects the upper calf muscles to the back of the heel bone. Achilles tendinitis is an injury to this tendon that causes pain in the back of the leg. Typically this injury results from inflammation of the surrounding sheath (paratenonitis), degeneration within the tendon (tendinosis), or a combination of the two.

Ailments of the Heel
Achilles Tendinosis
The Achilles tendon is the largest tendon in your body. It connects the upper calf muscles to the back of the heel bone. Achilles tendinosis is a condition in which the Achilles tendon degenerates and becomes inflamed. Sometimes, it may also be called Achilles tendinitis. If you have Achilles tendinosis, your tendon can swell and become painful. This condition is common in athletes, runners, and people who have calf tightness. Achilles tendinosis may occur in the middle of the tendon (known as midsubstance Achilles tendinosis) or at the point where the tendon connects to the heel bone (known as insertional Achilles tendinosis).
Heel Pain
Every mile you walk puts tons of stress on each foot. Your feet can handle a heavy load, but too much stress pushes them over their limits. When you pound your feet on hard surfaces playing sports or wear shoes that irritate sensitive tissues, you may develop heel pain, the most common problem affecting the foot and ankle.
A sore heel will usually get better on its own without surgery if you give it enough rest. However, many people ignore the early signs of heel pain and keep on doing the activities that caused it. When you continue to walk on a sore heel, it will only get worse and could become a chronic condition leading to more problems.
Plantar Fasciitis
If your first few steps out of bed in the morning cause severe pain in the heel of your foot, you may have plantar fasciitis, an overuse injury that affects the sole of the foot. A diagnosis of plantar fasciitis means you have inflamed the tough, fibrous band of tissue (fascia) connecting your heel bone to the base of your toes.
Plantar Fibroma and Plantar Fibromatosis
A plantar fibroma is a benign (non-cancerous) nodule that grows in the arch of the foot and usually appears between ages 20 and 60. It usually is slow-growing and often less than one inch in size. Some can grow faster and are considered plantar fibromatosis. A plantar fibroma or fibromatosis is a disease of the fibrous tissue that grows between the skin and the underlying fascia.