Achilles tendinitis is inflammation, irritation, and swelling of the Achilles tendon (the tendon that connects the muscles of the calf to the heel).

There are two large muscles in the calf, the gastrocnemius, and soleus. These muscles generate the power for pushing off with the foot or going up on the toes. The large Achilles tendon connects these muscles to the heel.

These are important muscles for walking. This tendon can become inflamed, most commonly as a result of overuse or arthritis, although inflammation can also be associated with trauma and infection.

Tendinitis due to overuse is most common in younger individuals and can occur in walkers, runners, or other athletes, especially in sports like basketball that involve jumping. Jumping places a large amount of stress on the Achilles tendon.

Tendinitis from arthritis is more common in the middle aged and elderly population. Arthritis often causes extra bony growths around joints, and if this occurs around the heel where the Achilles tendon attaches to the heel bone, the tendon can become inflamed and painful.

Symptoms usually include pain in the heel when walking or running. The tendon is usually painful to touch and the skin over the tendon may be swollen and warm.

Achilles tendinitis may make you more likely to have an Achilles rupture. This condition usually causes a sharp pain, like someone hit you in the back of the heel with a stick.

On physical exam, a doctor will look for tenderness along the tendon and for pain in the area of the tendon when the patient stands on their toes.

Imaging studies can also be helpful. X-rays can help diagnose arthritis and an MRI will demonstrate inflammation in the tendon.