UCL (ulnar collateral ligament)

The ulnar collateral ligament (UCL) is a thick band of tissue on the inside of the elbow that connects the humerus (upper arm bone) to the ulna (one of the forearm bones). It helps stabilize the elbow joint, especially during violent or repetitive throwing motions, such as in baseball pitchers. When the UCL is stretched or torn due to overuse or trauma, it can cause pain, instability, and loss of function. Treatment may include rest, physical therapy, or surgery, such as ligament reconstruction, to restore stability and allow return to activity.