My ankle frequently gives way underneath me from an injury I had years ago. The doctor tells me it is "unstable" but what does that mean exactly? What's going on?

There are two kinds of ankle instability. The first is called mechanical instability. This refers to an ankle that is unsteady for physical reasons--either the joint is loose or the ligaments are torn.

The second type of instability is called functional. No damage to the joint structures can be found but the ankle isn't stable during movements. With functional instability there may be a loss of joint position sense or decreased strength.

People with ankle injuries can have one or both of these kinds of instabilities. In fact instability is very common after lateral ankle sprains. A lateral ankle sprain affects the ligaments along the outside edge of the ankle.

A rehab program is usually advised to restore strength, motion, and joint position sense. Such a program can help you regain normal function of the joint and prevent any further giving-way episodes.