A sprain refers to an injury to the tissues surrounding and supporting a joint. This includes the ligaments and joint capsule. The ligaments are strong structures that prevent a joint from going into an abnormal position. The capsule is less strong and acts to seal the joint from the other tissues. A sprain can be of varying degrees. In a minor sprain the tissues essentially remain intact and recover rapidly, in a more serious sprain the tissues may be badly torn and sometimes need to be repaired surgically.
The commonest joint to be sprained is the PIP joint. The ligament that is injured most often is called the volar plate (palmar plate). This ligament prevents the joint from over straightening. The volar plate is damaged when force is applied in a longitudinal direction for example a ball hitting the end of the finger and the joint is forced into hyper-extension.
After a sprain the injured joint will become swollen, painful and stiff. The amount of swelling usually reflects the degree of injury.