Achilles tendinitis is an overuse injury of the Achilles tendon, which is the band of tissue that connects calf muscles at the back of the lower leg to your heel bone. It occurs when the tendon becomes swollen and painful near the bottom of the foot. The condition is caused by repetitive or intense strain on the Achilles tendon, which is used when walking, running, jumping, or pushing up on your toes. The pain associated with Achilles tendinitis typically begins as a mild ache in the back of the leg or above the heel after running or other sports activity. Episodes of more severe pain may occur after prolonged running, stair climbing, or sprinting. You might also experience tenderness or stiffness, especially in the morning, which usually improves with mild activity.

Achilles tendinitis is typically not related to a specific injury but results from repetitive stress to the tendon. This often happens when we push our bodies to do too much, too quickly. Other factors can also make a person more likely to develop Achilles tendinitis, including age, sex, flat feet, medical conditions such as psoriasis or high blood pressure, and certain medications such as fluoroquinolones.

If you experience persistent pain around the Achilles tendon, you should call your doctor. Seek immediate medical attention if the pain or disability is severe, as you may have a torn (ruptured) Achilles tendon. In most cases of Achilles tendinitis, nonsurgical treatment options will provide adequate pain relief, although it may take a few months for symptoms to completely subside. Even with treatment, the tendon may take longer to heal than other types of injuries due to its poor blood supply.