A sprain is a partial injury to a ligament. Ligaments form the connections between the different bones in the wrist. Ligament sprains range from mild stretches to partial tears.
There are many ligaments in the wrist that can be sprained. Two of the common ones are the scapholunate ligament, in the middle of the wrist between the scaphoid and lunate bones, and the TFCC (triangular fibrocartilage complex) on the outside of the wrist. Sometimes, a sprained wrist can pull off a tiny piece of bone. This is called an avulsion fracture.