DR MUIRIS HOUSTON DOCTOR ON CALL I PLAY a lot of sports in and outside of school and rarely get injured. But during a match last week I sprained my knee. What's the best way to treat a sprain?

LIGAMENTS ARE the strong tissues that connect bones together at a joint, giving it support. Sudden or violent movement can cause a sprain by tearing some of the ligament's fibres. When a ligament sustains a full tear then it is called a rupture.

A sprained ligament causes inflammation, swelling and often bleeding - which can be seen as bruising - around the affected joint. Movement can be extremely painful. Treatment is aimed reducing the inflammation and swelling, minimising pain and returning the joint to normal service as soon as possible.

During the first 24 hours following a sprain you should use the Rice principle, which stands for Rest, Ice, Compression and Elevation.

Resting the joint for the first 48 hours after injury allows the tissues to heal and the bruising to subside.

Applying ice to the injury helps to reduce blood flow to the damaged area and reduces swelling, bruising and pain. It should be applied as quickly after the injury as possible but never directly to the skin as it may cause an ice burn. Instead wrap the ice in a cloth and apply it gently to the injured joint.

Ideally this should be done for between 10 to 30 minutes initially.

During the first 48 hours, you may need to reapply the ice for 10 minutes every two hours while you are awake.

Using a bandage or tubular compression bandage helps limit swelling and rests the joint, allowing it to heal. But make sure it's not too tight as it could prevent blood flow.

Elevation of the injury will also help limit swelling. If you sprain your knee or ankle, you should use a pillow to rest your foot on while in bed. Anti-inflammatory medication may help reduce pain and swelling.

After 48 hours you can start gently exercising the joint several times a day.

Vigorous exercise is not recommended until the sprain has healed completely, which, depending on its severity, could take a number of weeks.

While compression bandages are not usually advised after the first 48 hours, a support bandage for the knee and ankle may sometimes be recommended to minimise swelling and keep the injured joint comfortable during activity.

If the injury is severe or there is any doubt about the diagnosis you should see your doctor. You may need to see a physiotherapist with an expertise in treating sports injuries if the problem doesn't settle.

Dr Muiris Houston is Medical Correspondent of The Irish Times. Queries to sportsdoctor@irish-times.ie