Swelling due to a broken ankle can last anywhere from a few months to a year, according to About.com and HealthTap. The duration of the swelling depends on the severity of the break, whether surgery is performed and any other treatment received.
The Tucson Orthopaedic Institute points out that swelling after ankle surgery on a fractured ankle is likely to last several weeks. Swelling can be reduced through elevating the ankle higher than the hip. Applying ice to the ankle also alleviates swelling, as do anti-inflammatory medications. The ankle is likely to remain somewhat swollen for up to six months after surgery. Once the ankle is able to bear some weight, swelling is likely to go down.