"This is a developmental, genetic predisposition to a certain shape of the hip joint that occurs during the first 15 years of development," Kelly said. "This is not related to steroid use. Steroids don't change the shape of your hip joint. This is a very well-known developmental phenomenon."
The procedure will be performed in New York, take approximately two hours and will be the second in the past five years for Rodriguez, who also had his right hip repaired by Vail, Colo.-based specialist Dr. Marc Philippon before the 2009 season.
Because of that previous procedure, plus the more involved nature of this newest surgery, Rodriguez has been following a prehabilitation program at Kelly's direction to strengthen the hip and speed his recovery.
Mariano Rivera similarly followed a "prehab" regimen after suffering a right knee injury in May. If Rodriguez had undergone the surgery when the issue was first diagnosed in November, for example, he would have been doing so with more inflammation in his hip.
"Operating earlier actually will frequently result in a more prolonged recovery afterwards, because it takes longer for the muscles to respond and recover from the surgery," Kelly said. "So the ultimate issue is not, 'Let's do surgery as soon as possible,' but 'What's the best strategy to get somebody back to full function the fastest?'"
Kelly said the cumulative effect of Rodriguez's injury robbed him of his internal rotation in the hips, which likely explains why A-Rod told coaches he was feeling a lack of explosiveness swinging the bat in the playoffs.
Examinations showed that Rodriguez's femur head -- which operates in the ball-and-socket-like function of the hip -- developed as more oval-shaped than a perfect round circle, which eventually caused it to tear into the labrum and affect the surrounding cartilage.
To repair that damage, Kelly said the procedure will involve making three small incisions in Rodriguez's hip and inserting a camera to assess the damage.
An anchor will be placed into the top of the hip to reattach the torn labrum, Kelly will shave the femoral head to a rounder shape to provide greater range of motion, and then repair as much cartilage damage as possible.
"We can definitely fix two of the three problems, the impingement and the labrum," Kelly said. "One thing is certain, the less permanent damage you have to the cartilage, the greater the probability is for return to pre-injury level of play."
While Kelly estimates that Rodriguez will be able to return to be productive during the 2013 season, that will largely stand as a guess until Rodriguez is examined on the operating table.
"I like to tell people six months is a reasonable time frame for return to play when we're doing the procedure we're discussing with a bone correction," Kelly said. "Optimistically speaking, what we're hoping for is for him to be able to return after the All-Star break."