Tommy John surgery is a procedure that replaces a torn ligament on the inner side of the elbow with a tendon taken from elsewhere in the body. It’s named after the Los Angeles Dodgers pitcher who first underwent the operation in 1974, and it has since become one of the most common surgeries in professional baseball. Up to 25% of Major League Baseball pitchers have had the procedure, with roughly 80% to 87% returning to their pre-injury level of performance.
The Ligament That Makes Throwing Possible
The ulnar collateral ligament, or UCL, is a small band of tissue on the inside of the elbow that connects the upper arm bone (humerus) to the lower arm bone (ulna). Its job is to keep the elbow stable when force pushes it sideways. When the elbow is bent, the UCL provides about 54% of the resistance against that sideways stress.
Throwing a baseball, especially pitching, creates enormous sideways force on the elbow during the cocking phase of the motion, right before the arm accelerates forward. Every pitch stretches the UCL near its breaking point. Over hundreds or thousands of throws, the ligament accumulates microscopic damage. Eventually, that damage adds up until one pitch causes a pop or tearing sensation on the inner elbow, followed by sharp pain. That’s typically the moment the UCL fails. Some tears happen gradually, with weeks of soreness before a final snap, while others seem to come out of nowhere on a single throw.
How the Surgery Works
Because the UCL can’t reliably heal on its own once it’s fully torn, surgeons replace it with a tendon graft harvested from elsewhere in the patient’s body. The most common source is the palmaris longus tendon in the forearm, a thin tendon that many people have but don’t functionally need. Hamstring tendons and big toe extensor tendons are also used.
The surgeon drills small holes into the humerus and ulna, the two bones the original ligament connected. The replacement tendon is then threaded through those holes and secured with sutures, buttons, or screws. Two threading techniques dominate: the docking technique and the figure-eight technique. Both aim to recreate the original ligament’s path so the new graft stabilizes the elbow the same way. If the ulnar nerve (the “funny bone” nerve that runs along the inner elbow) is irritated or at risk, the surgeon may move it to a safer position during the same operation.
Where the Surgery Came From
In July 1974, Tommy John felt a twinge in his pitching arm and could no longer throw. Dr. Frank Jobe, an orthopedic surgeon for the Dodgers, attempted an experimental procedure to reconstruct the ligament. It had never been done before, and Jobe estimated the odds of success at roughly 1 in 100. John missed the entire 1975 season recovering, returned to the mound in 1976, and kept pitching until 1989, winning 164 more games after the surgery. That improbable success turned the operation into a standard part of baseball medicine.
Recovery Takes About a Year
Immediately after surgery, the elbow is locked in a brace at a 60- to 90-degree angle to protect the graft while it heals. Pain, swelling, and stiffness are expected. Around seven to ten days out, patients begin a gentle range-of-motion program and switch to a removable brace. Within two weeks, an occupational therapist starts a regimen to gradually restore flexibility and build strength in the arm and shoulder.
The brace typically comes off completely around six weeks. The initial recovery phase, focused on managing swelling and regaining basic movement, lasts six to eight weeks total. After that, rehabilitation shifts toward rebuilding throwing strength. A structured throwing program begins several months later, progressing from short, easy tosses to long toss to throwing off a mound. Full recovery often takes nine months or longer, and most professional pitchers don’t return to competitive games for 12 to 16 months.
Return-to-Play Rates for Pros
The surgery has a strong track record. About 89% of MLB pitchers who undergo the procedure return to play, and a systematic review of over 1,500 MLB pitchers found that 79% to 87% returned to their pre-injury level based on in-game statistics. Those numbers are encouraging, but they also mean roughly one in five to one in ten pitchers never fully regain their prior form.
There’s a persistent belief that pitchers throw harder after Tommy John surgery. The reality is more nuanced. Pitchers whose ligament tore near the bottom of its attachment tended to already throw harder before their injury (averaging 93.0 mph versus 90.6 mph for those with tears near the top). Pitchers with tears near the top of the ligament did see their velocity and performance improve after reconstruction, essentially catching up to the higher-velocity group. The surgery itself doesn’t add velocity. What likely happens is that pitchers spend months in structured rehab strengthening muscles they may have neglected, and they return to the mound pain-free for the first time in a while.
Why So Many Young Players Are Getting Hurt
UCL injuries used to be concentrated among professionals in their late 20s and 30s. Now they’re increasingly common in high school and college players. The single biggest risk factor in youth athletes isn’t pitch count or throwing curveballs. It’s year-round play.
A prospective MRI study of young pitchers found that playing more than eight months per year was the factor most strongly associated with abnormal findings in the elbow. Neither position played nor pitch count correlated with MRI changes in that study. Two of the three most severe abnormalities (including a UCL tear) appeared in players who had pitched fewer than two innings the entire season but played year-round. Other research has confirmed that pitchers with shoulder and elbow injuries threw significantly more months per year, games per year, and pitches per year than their healthy peers. Pitching for multiple teams, which often leads to playing more total months, is another recognized risk factor.
Pitch count limits in youth leagues are reasonable, but they may not address the core problem. Arms need rest, and the offseason exists for a reason. Giving the elbow two to four months per year completely away from throwing appears to be the most protective measure young players can take.
Repair Versus Full Reconstruction
Not every UCL injury requires a full Tommy John reconstruction. A newer option called UCL repair with internal brace has emerged for certain patients. Instead of replacing the ligament entirely, the surgeon stitches the torn ligament back together and reinforces it with a strong synthetic tape that acts as a scaffold while the tissue heals.
This approach works best for partial tears. In studies comparing the two procedures, players who received the repair had a higher proportion of partial tears and a lower proportion of complete tears compared to those who got a full reconstruction. The repair also tends to involve a shorter recovery timeline, which makes it appealing for athletes trying to minimize time away from competition. For complete tears, full reconstruction with a tendon graft remains the standard.