Tommy John surgery is the surgical reconstruction of elbow ligaments (UCL) often torn by pitchers. The elbow ligament is replaced with a tendon from the forearm, hamstring or knee.
In 1974, Tommy John (Los Angeles Dodgers) felt elbow discomfort and was unable to pitch. The ligament John injured was the ulnar collateral ligament (UCL), which is on the inside of the elbow joint, and where the pain is felt. Prior to John receiving the surgery, this was a career ending injury.
Tommy John surgery has come a long way and most pitchers make successful returns to the mound. Rehab normally takes 12-18 months.