My Mother has developed a bed sore on the outside of her right ankle. Any advice?

That's also a prime spot for venous stasis ulcers, which are managed differently. That's what it might be if she has varicose veins and/or edema of the ankles, and it won't go away with just relieving pressure. You actually have to put a dressing on it and use compression, which you would NOT do for a pressure sore.

If it is a real pressure sore, keeping pressure off as everyone else suggests is critical, and assessing nutrition in particular protein store is important too.

You can elevate her foot with a pillow, making sure not even the sheet touches the sore. There is also a cushiony ankle protector you can use ... bed sores are nothing to play with. If you see the slightest red mark developing protect the area as quickly as possible.

I've seen home care nurses roll up a soft towel and put it under the ankle. In the hospital, when a patient is lying on his or her back, nurses have also done the same thing, using really soft blankets that don't abrade the skin.

Does she sleep on a hospital bed? If so, you might ask her doctor to script for an alternating pressure mattress. It's electrical and when turned on alternately raises and lowers specific sections of the mattress to prevent skin from being in contact too long with a flat mattress surface.

My father used one. I don't recall whether his doctor or the home care nurse recommended it.

It might be hard and a bit uncomfortable for your mother since she sleeps on that side. There might be some other treatments of which I'm unaware.

I assume your mother is getting treatment for the bed sore?