The medical term for a torn ligament is a sprain that happens when the ankle is twisted or injured in a fall. Sprains are extremely painful and require immediate medical attention to ensure that they heal correctly.
A partially torn ligament is a Grade II sprain and a completely torn ligament is Grade III. A Grade II will produce a looseness of the ankle joint, while a Grade III produces gross instability.
A Grade II sprain will cause pain when you put weight on your ankle and the joints might feel loose. With a Grade III sprain, you will be unable to put weight on your ankle or it will collapse.
Both sprains produce pain if you use or even touch your ankle. Grade II pain will feel like a tenderness, such as you would feel with a bruise. A Grade III sprain will be acutely painful upon touch or slight pressure.
Any sprain will produce swelling in the ankle. It also can cause bruising and discolouration, depending on the severity of the tear. The swelling might also affect circulation to the ankle.
Torn ligaments can cause you to lose the ability to feel someone touching your skin and you can have trouble moving your ankle, even with no weight on it.