Ankles take a beating. They take almost as much of a beating daily as feet do. However, there are times when your ankles cannot do what you need them to do, which is A) move, and B) control your feet so that your feet move and you are able to walk, run, etc.. Those are the times when you will need surgery, and an ankle surgeon can help. Here are some of the more common issues that require ankle surgery if your ankle will ever work properly again. 

Tears of the Achilles Tendon

The Achilles tendon connects the back of your heel to your calf muscle near your ankle. If it tears, only surgery can repair it. If it tears completely, your foot just flops around and you will be in such extreme pain that you will not be able to stand it. The former, lesser tears will be almost as painful, and you may have some limited mobility, but you should not move the foot or apply pressure at all because it could cause a complete tear. Even with surgery, it will take weeks for your ankle to heal. 

Breaks of the Lower Ends of the Tibia and Fibula

Your ankle is made up of the upper tarsal bones of the foot, with the lower ends of the tibia and fibula inserting behind the tarsal bones. If you break the lower ends of the tibia and/or fibula, your ankle will require surgery to put pins in these bones. The ends are very small compared to the size of the rest of these two bones, and breaking them means that they will not reset without having medical pins inserted.

Your ankle surgeon may also use an immobilization "cage" that surrounds the lower leg, with screws drilled through holes in the cage into the bones to help the leg bones stay in position until the broken bits mend properly. It will look positively medieval, and even be quite painful, but it works. 

Breaks in the Upper Tarsal Bones

Your foot is made up of dozens of bones, just like your wrists, hands, and fingers. The upper bones are called tarsals, and the lower bones reaching to the ends of your toes are metatarsals. All of the blood vessels and nerves that run from your lower leg into your foot and toes and back up again go through the tarsals. If you have a crush fracture that breaks some of the tarsals, the nerves might be compressed, and the blood vessels destroyed. Surgery is required to remove some of the pressure of the smashed bones on the nerves and the blood vessels should heal themselves.

If it is especially bad, the ankle surgeon may decide to graft bone to fix the damaged tarsals, use metal plates or 3D printed material to replace bones, or amputate, depending on the severity of the injury.