What Causes a Sprain?
A sprain can result from a fall, a sudden twist, or a blow to the body that forces a joint out of its normal position and stretches or tears the ligament supporting that joint. Typically, sprains occur when people fall and land on an outstretched arm, slide into a baseball base, land on the side of their foot, or twist a knee with the foot planted firmly on the ground.

Where Do Sprains Usually Occur?
Although sprains can occur in both the upper and lower parts of the body, the most common site is the ankle. More than 25,000 individuals sprain an ankle each day in the United States.

What Are the Signs and Symptoms of a Sprain?
The usual signs and symptoms include pain, swelling, bruising, instability, and loss of the ability to move and use the joint (called functional ability). However, these signs and symptoms can vary in intensity, depending on the severity of the sprain. Sometimes people feel a pop or tear when the injury happens.

Doctors closely observe an injured site and ask questions to obtain information to diagnose the severity of a sprain. In general, a grade I or mild sprain is caused by overstretching or slight tearing of the ligaments with no joint instability. A person with a mild sprain usually experiences minimal pain, swelling, and little or no loss of functional ability. Bruising is absent or slight, and the person is usually able to put weight on the affected joint.

When To See a Doctor for a Sprain
  • You have severe pain and cannot put any weight on the injured joint.
     
  • The injured area looks crooked or has lumps and bumps (other than swelling) that you do not see on the uninjured joint.
     
  • You cannot move the injured joint.
     
  • You cannot walk more than four steps without significant pain.
     
  • Your limb buckles or gives way when you try to use the joint.
     
  • You have numbness in any part of the injured area.
     
  • You see redness or red streaks spreading out from the injury.
     
  • You injure an area that has been injured several times before.
     
  • You have pain, swelling, or redness over a bony part of your foot.
     
  • You are in doubt about the seriousness of the injury or how to care for it.