The causes of Achilles tendon swelling and pain are Achilles tendon trauma, aseptic inflammation, and infection, as follows: First, Achilles tendon trauma: Achilles tendon trauma is a common cause of such symptoms, such as when jumping with force or after a direct violent blow to the Achilles tendon, it is very easy to tear the Achilles tendon, and then the patient will have swelling and pain in the Achilles tendon area. Second, aseptic inflammation: Some patients may have swelling and pain due to aseptic inflammation here, such as in the recent frequent heavy weight-bearing, it may be because the Achilles tendon long-term excessive strain or friction and inflammation, after which will also cause swelling and pain symptoms. Third, infection: some patients may suffer from infection, such as cellulitis in the soft tissues around the Achilles tendon, which may lead to swelling and pain.