I know quite a lot about bad ankles. in my experience, once seriusly sprained they're weak. i still remember when I did my right one - stepped on the #8's foot at the back of a rugby scrum, and turned it over. About 35 years ago, and it still can bother me.
Anyway, here's an interesting article in the NY Times health section a few days ago. And, there's a three minute video.
At the same time, in sports they’re the most commonly injured body part — each year approximately eight million people sprain an ankle. Millions of those will then go on to sprain that same ankle, or their other ankle, in the future. “The recurrence rate for ankle sprains is at least 30 percent,” McKeon says, “and depending on what numbers you use, it may be high as 80 percent.”
A growing body of research suggests that many of those second (and often third and fourth) sprains could be avoided with an easy course of treatment. Stand on one leg. Try not to wobble. Hold for a minute. Repeat.
This is the essence of balance training, a supremely low-tech but increasingly well-documented approach to dealing with unstable ankles. A number of studies published since last year have shown that the treatment, simple as it is, can be quite beneficial.
Why should balance training prevent ankle sprains? The reasons are both obvious and quite subtle. Until recently, clinicians thought that ankle sprains were primarily a matter of overstretched, traumatized ligaments. Tape or brace the joint, relieve pressure on the sore tissue, and a person should heal fully, they thought. But that approach ignored the role of the central nervous system, which is intimately tied in to every joint. “There are neural receptors in ligaments,” says Jay Hertel, an associate professor of kinesiology at the University of Virginia and an expert on the ankle. When you damage the ligament, “you damage the neuro-receptors as well. Your brain no longer receives reliable signals” from the ankle about how your ankle and foot are positioned in relation to the ground.