The process begins when surgeons harvest a tendon from elsewhere in body. It is moved into the elbow and allowed to heal over time. The transformation is complete months later, when the tendon attaches to the bone and becomes a brand-new ligament.
Stan Conte, the Dodgers' vice president of medical services, has devoted years of study to the procedure commonly known as Tommy John surgery.
What the human body is capable of still leaves him in awe.
"That process is pretty [expletive] amazing," said Conte, his voice revealing a sense of wonder.
The transformation, however, takes time. And as simple as that sounds, it's a concept that Conte believes gets lost when it comes to the way players are viewed when coming off Tommy John surgery. It's an issue that has become particularly relevant to the Mets and their rehabbing ace, Matt Harvey.
At the team's complex in Florida yesterday, Harvey took a major step in his recovery by throwing a 20-pitch bullpen session in front of media and Mets officials after undergoing surgery a little more than nine months ago.
Harvey has long held out hope of making a return sometime in September -- giving him a recovery time of about 11 months. But the Mets have slowed his rehab, thus making it more likely that Harvey returns at the start of next season.
That might not be such a bad thing.
Speaking generally, Conte said there are risks involved with returning to competition less than 12 months after surgery. The biggest issue, he said, stems from competing with a ligament that is not yet fully formed.
With tears of the anterior cruciate ligament (ACL) in the knee, Conte said it is possible for doctors to check on the progress by removing tissue samples and examining them. From this, Conte said an ACL graft typically takes a year to "mature."
But he said it's tougher to gauge the progress of a ligament in an elbow. In that case, extra time is simply another safety measure.
"If it's not completely mature, and you ask it to do what it's supposed to do at 100 percent and it's only at 70 percent, you potentially have a problem," Conte said earlier this season.
While he said it's possible for pitchers to "get away with" an early return, Conte said there is reason to believe that a recovery time of 12 months or more is much more effective.
The conservative approach makes even more sense since ligament problems fall in the realm of what Conte considers "velocity injuries."
"You increase your velocity and you increase the stress on the ligament," he said. "That stress, that strut that's there, has to take that force so it doesn't break."
Harvey conceded to some concern about trying to come back too quickly, though he has insisted throughout the process that he felt physically strong.
"The last thing you want to do is jeopardize your career or 2015," Harvey said. "But everybody's trying to do their best to figure out what's the right time and exactly what's causing this injury this frequently. I felt great the whole time and it feels normal. It feels like nothing happened."
Conte called the perception of a 12-month recovery period for Tommy John surgery "a myth," one that he hopes changes now that a rash of elbow injuries has shed light on the problem.
"When we start seeing some of these guys with a second Tommy John, it worries me as the guy who does the rehab that we're going too fast," Conte said. "I don't want the perception to be that everybody comes backs at 12 months, and if they come back at 14 months, they're behind schedule. We do this all the time. Everybody quotes the same thing. It's 12 to 18 months. But nobody pays attention to the 18 months."
Said Conte: "From a safety standpoint, I'd rather go longer than shorter."