A sprain is an injury that damages a ligament. A ligament is a firm, fibrous band of tissue. It connects two bones across a joint. There are ligaments crossing all of the joints in the body.

Grade 1 and 2 sprains are less severe. The internal structure of the ligament in damaged but the ligament remain intact. Grade 3 sprains are more severe. They include complete tears of the ligament. Grade 3 sprains are sometimes called torn or ruptured ligaments.

Sprain: Grade 2
Nucleus factsheet image
Copyright © Nucleus Medical Media, Inc.

The most common joints involved include:

  • Ankle
  • Knee
  • Thumb or finger
  • Shoulder (acromioclavicular joint)

A sprain occurs when a force pushes the bones of a joint apart. If the force is intense enough, the ligament holding the joint together has to give. Actions that may cause a sprain include:

  • Sudden change in direction
  • Impact with object or other person
  • Misstep that causes sudden strain at joint