Achilles tendonitis causes inflammation and degeneration of the achilles tendon. The achilles tendon is the large tendon located in the back of the leg that inserts into the heel. The pain caused by achilles tendonitis can develop gradually without a history of trauma. The pain can be a shooting pain, burning pain, or even an extremely piercing pain. Achilles tendonitis should not be left untreated due to the danger that the tendon can become weak and ruptured.Achilles Tendonitis is aggravated by activities that repeatedly stress the tendon, causing inflammation. In some cases even prolonged periods of standing can cause symptoms. It is a common problem often experienced by athletes, particularly distance runners. Achilles Tendonitis is a difficult injury to treat in athletes due to their high level of activity and reluctance to stop or slow down their training.Individuals who suffer from achilles tendonitis often complain that their first steps out of bed in the morning are extremely painful. Another common complaint is pain after steps are taken after long periods of sitting. This pain often lessens with activity.