Foot and Ankle Surgeon, Jeremy McCormick, MD:
Ankle sprains are the most common foot and ankle injury in sports. Typically, sprains occur when inverts with an awkward step while running or jumping. As the foot rotates inward, the ligaments on the outside, or lateral aspect of the ankle, are stretched, causing swelling and pain. Most frequently, sprains will recover completely with rest, ice, compression, evaluation and early mobilization.
In less than 10% of cases, while ankle swelling and pain improves, the ankle continues to "give out" or feel unstable. Classically, this occurs when walking on uneven ground or when stepping off a curb. Repeated episodes of "giving out" is a condition called chronic ankle instability. Most frequently, this is a result of incomplete recovery from an acute ankle sprain that leaves the ankle with weakness and impaired postural control.
The initial treatment for chronic ankle instability is a program of structured rehabilitation with the help of a physical therapist. Exercises are aimed specially at strengthening the peroneal tendons which run on the outside aspect of the ankle. The regimen should also include use of a balance board or similar device to work on proprioception - awareness of the position of the foot and ankle in space. Improved proprioception helps the ankle react more quickly to stresses, preventing future sprains.
After 6-8 weeks of intensive therapy, if the ankle continues to feel unstable, one might be a candidate for surgery to reconstruct the injured ankle ligaments. At this point, an MRI is helpful to identify any underlying injury such as cartilage damage at the ankle or peroneal tendon tears. Complete recovery from surgery takes at least 3 months, but patients will typically be able to return to full activity without limitation, and, most importantly, without the sensation of their ankle "giving out."