While there are a number of ligaments around the elbow that provide stability, the most commonly injured is the medial ulnar collateral ligament (UCL or Tommy John ligament). This ligament is on the inside (medial) part of the elbow that is closest to the body. Although injury to the medial ulnar collateral ligament (Tommy John ligament) is most commonly thought of in overhead throwing athletes (i.e., baseball, softball, or javelin throwers), it can also occur in gymnasts, wrestlers, football players, or other contact athletes.

These injuries can be the result of a sudden, acute injury, or they can occur following long periods of overuse. Injuries to the UCL can vary significantly in severity as the ligament can tear partially or completely, and it can tear in different locations (proximal, distal, or mid-substance). All of these factors must be taken into consideration when determining the optimal treatment strategies for UCL injuries.

In recent years, there have been significant increases in the rates of UCL injuries. Accordingly, in addition to studying the optimal treatment strategies of these injuries, much of the research performed by the Mayo Clinic Orthopedics and Sports Medicine team is focused on injury prevention and identifying athletes at risk.