DEAR DOCTOR K:

I recently sprained my ankle. I know I twisted it and that it hurts when I walk on it, but what exactly happened to my foot?

DEAR READER:

Many people use the words "sprain" and "twist" interchangeably. Though you may sprain your ankle by twisting it, the words do not mean the same thing. A sprain is a tear of ligaments, which are the tough bands of fibrous tissue that connect bones to one another at a joint.

Your ankle is the meeting place for a bunch of bones. There are the two long bones of your lower leg and a group of small bones in the foot. They're all connected to give the ankle flexibility and the strength it needs to support your weight.

It's the ligaments connecting these bones that give the ankle both flexibility and strength. The ligaments stabilize a joint. When a joint is sprained, its torn or stretched ligaments can lose part or all of their ability to reinforce the joint and to keep it moving normally. In severe cases, the sprained joint can become unstable and loose.

A common ankle sprain is caused by an inversion injury. To get a sense of how this happens, sit down and place your right foot on the ground. Then move your knee outward (to the right). Feel how the weight no longer is on the sole of your foot? Instead, it's on the outer side of your foot. If that happens when you're standing, your ankle will suddenly turn and injure ligaments.

Sprains cause pain and swelling. Additional symptoms depend on the severity of the sprain:

-- A mild sprain causes only microscopic tears in a ligament. These tiny tears can stretch the ligament and cause some pain, but they do not significantly affect the stability of the injured joint.

-- With a moderate sprain, the injured ligament is partially torn, and there is mild to moderate joint instability.

-- With a severe sprain, the ligament is either torn completely or pulled away from the place where it attaches to bone. There is significant joint instability.

How long a sprain lasts depends on many factors, including its location and severity. If you have a mild or moderate sprain, your doctor probably will recommend the RICE rule:

-- Rest the joint.

-- Ice the injured area soon after the injury to reduce swelling.

-- Compress the swelling with an elastic bandage.

-- Elevate the injured joint.

A temporary sling or a brace, along with a nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen (Advil, Motrin, others), can also help. As joint pain subsides, a rehabilitation program can help to strengthen the muscles around your injured joint, reducing your risk of reinjury.

Treatment for a severe sprain depends on which ligament has been torn. Some torn ligaments can be repaired surgically with stitches; others must be replaced surgically. Still others are treated with rehabilitation and a temporary cast or brace.

(Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.)

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