The tendon at the back of the heel is called Achilles tendon, and the tendon pain at the back of the heel is actually Achilles tendon pain, which has various causes, such as Achilles tendon injury, Achilles tendonitis, plantar fasciitis and sciatica. 1. Achilles tendon injury: when running and jumping, the Achilles tendon is strained or hit, resulting in trauma to the Achilles tendon, causing edema or even rupture of the Achilles tendon, which can cause pain in the back of the heel. 2. Achilles tendonitis: generally refers to the formation of aseptic inflammation of the Achilles tendon after acute and chronic strain. As a result of not warming up before exercise, over-exercise, prolonged walking or hiking, etc., the Achilles tendon is pulled for a long period of time, resulting in localized chronic tearing, causing aseptic inflammation, which leads to pain inside and above the heel. In addition, the arch of a flat foot increases the risk of Achilles tendonitis. 3. Plantar fasciitis: Strain and inflammation of the plantar tendon membrane is mainly caused by running and aerobics, especially when wearing inappropriate shoes. It manifests as pain in the plantar and heel areas. 4. Sciatica: Sciatica is a syndrome characterized by pain in the pathway and distribution area of the sciatic nerve. The pain starts from the waist, buttocks or the back of the thigh and radiates to the distal lower limbs, and even the heel tendon pain. The Achilles tendon is easy to be injured, early after the discovery of heel tendon pain, you should go to the hospital, relevant examination, in order to clarify the cause of the disease, timely treatment.