On a conference call with Yankees beat writers, Dr. Bryan Kelly spoke for more than a half an hour this afternoon, trying to explain the details of what's already happened to Alex Rodriguez's left hip and what's about to happen to it. Here's an attempt to give you the basics of those details.

What exactly caused this problem?

Basically, the top of Rodriguez's femur is misshapen, and it's been misshapen for 20-plus years. The top of his hip isn't perfectly round, which means it doesn't fit perfectly into the hip socket.

"This is a condition that occurs during the developmental phase of the formation of the hip joint between the ages of birth to anywhere between 14 and 15 years," Dr. Kelly said. "The reasons why you develop impingement has got to do with two things: the genetics of their hip and the mechanical forces that the hip is subjected to during the first 15 years of development, where growth occurs in something called the growth plate. A remodeling process can occur that leads to a non-spherical femoral head and the hip itself is designed to (resemble) a ball-bearing joint, a ball-and-socket joint. If you have a non-spherical head, which is very common in athletes both male and female, the anatomy of the hip limits the amount of functional motion that can occur in the hip joint."