Moss underwent an MRI on Monday after requesting one during his exit interview at PNC Park last week. The request came not as a result of any recent pain, but because Moss had bypassed the option of having his knee checked out in late June-early July. It was at that time Moss complained of some minor discomfort while playing a series on the Rays' Astroturf field.
Moss took anti-inflammatory medicine to remedy the problem then, and he has not felt any discomfort since.
Still, just in case, he decided to have his knee checked out.
"It kind of caught me off guard with the results that came back," Moss said. "The results that came back are not what I feel. It hasn't bothered me since June. If it would have been bothering me while I was playing, I would have said something and had it taken care of a lot sooner."
What the results showed is medically defined as osteochondritis dissecans. In layman's terms, the MRI revealed that at the location of Moss's knee joint, his tibia and fibula bones have rubbed together and are creating a divot that can cause cartilage to separate from the bone.
A microfracture procedure is typically recommended to surgically take care of the problem. A number of high-profile athletes -- including the NBA's Greg Oden, Amare Stoudemire and Jason Kidd -- have undergone this procedure.
Because such surgery requires a lengthy recovery process -- eight weeks with no weight put on the leg, followed by four to six months of rehab -- Moss will seek a second opinion later this week from knee specialist Dr. Richard Steadman in Vail, Colo., before agreeing to surgery. Steadman is credited with developing the microfracture procedure about 20 years ago.
"I'm definitely going to explore any options that I can, [and] see if surgery is the only option," Moss said. "Obviously, they're doctors, and they know more about my body than I do. But I know how it feels. It doesn't bother me. I'm playing at 100 percent."
Moss will return to Pittsburgh on Wednesday to consult with DeMeo again before heading out to Vail on either Thursday or Friday.
Manager John Russell has not yet ruled Moss inactive for the rest of the season, though the outfielder was out of the lineup Tuesday. Russell said he will wait until after Moss' visit to Steadman before making any decisions about Moss possibly playing in this weekend's series.
Neither Russell nor Moss attributed the knee injury to Moss' below-average offensive numbers. Since coming over to Pittsburgh from Boston in a July 31 trade, Moss has hit .222 with six homers and 23 RBIs in 158 at-bats.
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.