Hammel is expected to be placed on the disabled list tomorrow, and he could make his decision before leaving Camden Yards.
Hammel said the MRI taken today didn't reveal any new damage, but the cartilage has floated to a location where it's pressing against a nerve whenever he bends the knee.
Manager Buck Showalter suggested that Hammel could return by early September if he undergoes the arthroscopic procedure.
Update: "The MRI found there was no further damage to what I've been dealing with for the last couple months, which was good," Hammel said. "That's a positive. The only problem is the cartilage that was floating around in there is in a bad place right now, so we're going to consider our options, see what we have. Surgery is an option. Could let it rest, too. At this point, I will probably know more tomorrow.
"For about a month after it happened, it was pretty serious, but there for a while I started seeing some progress in the right direction, and at the All-Star break it felt great. And for the workouts we came in Thursday, and it was awesome. It surprised me. It was just on that one pitch (Friday)."
The piece of cartilage has lodged in a bad area.
"Where it was before, it was kind of uncomfortable," Hammel said. "Now it's kind of in the joint, kind of pinned into the joint, so every time I bend the knee it pretty much hits the nerve in the area, so it's not very comfortable right now.
"Honestly, I just want my knee to feel normal again, so I'm kind of leaning toward surgery, but I haven't made that decision yet."
Hammel can't wait much longer to decide.
"It's got to be soon, because I don't want to miss too much time," he said. "It's a pretty simple procedure to go in there and just let it be scoped, but like I said, I could let it rest and it could be fine that way, but it'd be better just to get it taken care of."
It's possible that the cartilage could float to another, less painful and restrictive part of the knee, "but then there's also the problem of damaging more instead of just having the condition we have right now," he said.
"It's very tough. I feel like I'm letting the guys down if I miss starts. I want to be part of this. It's tough because my body is letting me down right now and I feel so good. A lot of hard work to get where we are right now. It is what it is. If something does happen, the other guys are going to step up. It'll be an opportunity for somebody else. And as soon as I can come back and help the team, I'm going to do that."
Showalter will decide tomorrow whether to place Hammel on the DL, which is more likely with the Orioles needing another pitcher.
"We got the tests back and he's considering his options, one of which is surgery," Showalter said. "Not a whole lot of changes from the previous MRI, just what his challenges were have moved a little bit to a spot that's a little more challenging. I think we'll bring it to a head tomorrow. He just wants to gather other opinions and decide, if he does something, where he'd do it. He just wants to get it where he's not thinking about it all the time.
"If it is a surgery, he still could be back, in a good scenario, in the first week of September. He would be a nice addition for us if we have to go in that direction. But we'll see."