A sprain is an injury to a ligament. Ligaments are the connective tissues that connect and stabilize one bone to another bone; they could be thought of as very strong tape that holds the bones together at a joint. The degree of ligament injury may vary over a wide range of severity.
Sprains are generally classified into three types:
Grade I – stable injury to a ligament;
Grade II – partial tearing/stretching;
Grade III – complete tear of the ligament, either within the mid-portion of the ligament, or as an avulsion (“pulling away”) from its attachment into bone. A sprain may upset the normal coordinated movements of the wrist bones resulting in persistent stiffness, pain, swelling, and possible instability.