The 33-year-old suffered an injury he described as "a tear" to his right side against Taylor Fritz in the third round, but was fit enough to beat Milos Raonic 7-6(4) 4-6 6-1 6-4 in the early hours of Monday morning to reach the quarter-finals.
The world number one said he has been having extensive treatment and was on painkillers, but declined to actually explain what the injury was when asked.
"I did an MRI (scan), I did everything, I know what it is, but I don't want to talk about it now. I'm still in the tournament," Djokovic told reporters. "I hope you guys understand that. I don't want to speculate too much about it.
"I didn't know few hours before I stepped on the court tonight whether I'm gonna play or not.
"If I'm part of any other tournament other than a Grand Slam, I definitely wouldn't be playing."
Djokovic occasionally pulled up gingerly against Raonic although he struck the ball with his usual power and precision.
"It's kind of a gamble, that's what the medical team told me. It's really unpredictable," Djokovic said.
"It could cause much more damage than it is at the moment, but it also could go in a good direction. That's something that I don't know, and I don't think I will know until I stop taking painkillers. As long as I'm with high dose of painkillers, I guess I still can bear some of the pain.
"But the tricky thing with the painkillers is that they hide what's really happening in there, so you might not feel it, but then the big damage might be done."
Djokovic will face a potentially tougher test against German sixth seed Alexander Zverev on Tuesday.
"Playing against Sascha is a different matchup, there's probably going to be more rallies, gruelling rallies, exhausting, and it's going to be demanding from my side really from back of the court," Djokovic said.
Meanwhile, third seed Dominic Thiem slumped out of Grand Slam in lacklustre fashion, complaining of undisclosed physical issues after being thrashed 6-4 6-4 6-0 in the fourth round by Grigor Dimitrov.
The U.S. Open champion, who came back from two sets down to beat Nick Kyrgios in a third round battle on Friday night, looked out of sorts from the beginning of the contest and made an uncharacteristic 41 unforced errors.
"A combination of some little physical issues, plus a real bad day, plus the fact that he's a great player ... a result like that can happen," Thiem said.
"I'm not a machine, sometimes I would like to be, but there are really, really bad days. As soon as you're not 100% at this level, then results like this come up, and that's exactly what happened today."
While Thiem's five-set match against Kyrgios had been played in a bear pit, Sunday's match was witnessed by only a handful of officials and coaches on Rod Laver Arena as Melbourne's coronavirus lockdown kept the fans away.
"It was a special match two nights ago, and I woke up maybe a little bit different than on a normal match, especially with all the energy from the crowd," Thiem added.
"But ... it didn't really affect me today."
On Sunday, the first two sets followed a similar pattern with Thiem taking an early 3-1 lead only for 18th seed Dimitrov to charge back at him and clinch the set.
The Austrian was unable to rouse himself in the third set and his Australian Open ended when he flapped a forehand long after little more than two hours on court.
"Throughout every season you have one of those matches where you keep the ball rolling," Dimitrov said.
"He might have had a problem, I don't know, but I also give myself some credit for staying in there. He's an extraordinary player so I'm happy with the win."
After securing his maiden Grand Slam crown at Flushing Meadows last year, Thiem had been widely tipped to challenge Novak Djokovic, Rafa Nadal and Roger Federer for more major titles this year.
Dimitrov knows all about failing to fulfil big expectations after being dubbed "Baby Fed" early in his career for the similarity of his playing style to that of Federer.
The 29-year-old took Nadal to five sets in the 2017 semi-finals at Melbourne Park but has never played a Grand Slam final.
Dimitrov will play Russian qualifier Aslan Karatsev, the world number 114, in his fourth Australian Open quarter-final later this week but was taking nothing for granted.
"If you're there, it's for a reason, whether it's a fairytale or not, you've got to be ready. It's going to be a battle," Dimitrov said.