Gibson says it's the same MCL he sprained in late February, keeping him sidelined for a month, and he's hoping an MRI on Wednesday doesn't show anything more than that.
"That's what happens when you rush back and try to help your team win," a frustrated Gibson said after the Bulls' 90-86 loss to the Wizards.
"I've still got an MRI [Wednesday] but hopefully it's not as worse as before. But it was real painful ... it's similar. But it's all about how it's going to feel [Wednesday]. I hope there's no swelling. But that's what they said, the same injury, the same MCL sprain, but we don't know the [degree] just yet."
Gibson said the injury occurred while he was trying to guard Wizards swingman Trevor Ariza in the second quarter. Gibson came out of the game with 4:37 left in the half and hobbled straight back to the locker room.
"I just did a basic rotation," Gibson said. "Tried to slide, and it just buckled on me. It was real painful. I tried to just play through it because I kind of got nicked up the last couple games and kept playing. I came down the court and just told [coach Tom Thibodeau] to take me out and just went to the back. I just knew it was real painful, I just couldn't keep going. I didn't want to hurt my teammates."
Gibson struggled to put much weight on the knee as he exited the locker room.
"It's kind of difficult to put pressure on it, but that's how it is when you kind of sprain it. I'm just hoping that I have nothing torn but it basically feels the same as when I hurt it the first time," he said.
If Gibson were to go down for a long stretch again, his teammates know it will be hard to replace him. The Bulls are already playing without Marco Belinelli (ab strain), Rip Hamilton (lower back), Joakim Noah (plantar fasciitis) and Derrick Rose (knee).
"It's definitely another big blow," Bulls guard Kirk Hinrich said of Gibson's injury. "I don't know what else to say but we got to hang together, find some healthy bodies, and the guys that are out there are going to have to step up even more. We've been short-handed all year. It's nothing new to us, but we are trying to nurse him back to 100 percent. He wasn't 100 percent to begin with. We're going to have to find a way."