If a sprain is worse than severe, does it become a fracture (like an ankle fracture)? how are they related?

Trauma causes both: A sprain is a painful, traumatic stretch of a ligament or muscle. If severe it could rupture the tendon. Fractures occur from direct trauma, but not by extension of a sprain. For any of these ice the part involved and see an er doc or an orthopedic specialist to have it evaluated and proper treatment applied.

Fracture: Involves bone. A sprain involves ligament. If the sprain is sever the ligament may be torn. It is possible to have a fracture and a sprain.

A sprain is a sprain: A sprain will not lead to a fracture unless there is another injury. Immobilization will be of benefit to stabilize the area.