While we don't have specifics about his current conditions, last year, the Phillies said Utley had patellar tendonitis - also known as "Jumper's Knee," chondromalacia - also known as "Runner's Knee," and bone inflammation.
Action News spoke with a doctor who is not treating Utley, but is familiar with those conditions.
As the chief of Penn Medicine's sports medicine program, Dr. Brian Sennett has seen many patients with patellar tendonitis, and says it is an overuse injury, occurring more in veteran athletes than in young ones.
"The tendon kind of fatigues, it tires with a certain amount of exercise. It essentially gets some small microscopic tears in the tendon itself. They sometimes don't have a great blood supply. they don't heal real well," he explains.
And they can be painful, especially for baseball players.
"It is usually bent-knee activities, where it's jumping or quick push-offs. someone like chase where he's going to the right or the left fielding a ball, or, or, getting started out of the batter's box - any of these things are very common ways you can strain the patella tendon, and develop these small tendon tears that will go on to cause tendinitis," says Dr. Sennett.
He says patellar tendinitis usually comes from overuse, and the inflammation can cause sharp pain right below the knee cap.
Physical therapy, rest, and anti-inflammatory medications work 95% of the time.
That's what Utley did that last season and during the off season.
But the team says his rehabilitation has hit a plateau, and his knees aren't healthy enough to get back on the field.
Dr. Sennett says when patellar tendinitis goes on for more than a year, his experience shows that many times surgery can help.
"If an individual has a very focal, or a spot location, where they have that tendinitis, and that damage to the tendon, you can litterally cut out the damaged tendon, the body will create new tendon to that location, and it will often heal that area," he says.
As of now, the team has not talked about surgery, and Utley has said he would like to avoid it.
If someone were to have surgery for this type of tendonitis, he would have to sit out from any sport for about 3 months.
And any athlete with chronic patellar tendinitis has to consider the options carefully.
"It's gonna really be on how much his symptoms really bother him. the trainers can sometimes do taping, they can do certain kinds of straps that are helpful. but it really comes down to how much does the tendon still bother him when he steps on the field," Dr. Sennett says.
We'll have to wait and see what happens in Utley's case.
For more on the Penn Medicine sports medicine program, click here..