"If he's been released from the hospital he was in, it means he's able to support his own breathing and bodily functions," said Dr. Tipu Aziz, a professor of neurosurgery at Oxford University's John Radcliffe Hospital.
The fact that Schumacher is going into rehabilitation "suggests there's been long-term side effects of his injury," he added.
"With rehabilitation, they'll try to train him to cope with the disabilities that he's got to achieve as much life function as possible," Aziz said. "If he's had a brain injury, he may have weakness in his limbs secondary to loss of brain function. He may have problems with speech and swallowing."
He said that "rehabilitation would probably take a good few months" but noted that Schumacher was an athlete before his accident "so was in good shape."
Schumacher earned universal acclaim for his uncommon and sometimes ruthless driving talent, which led to a record 91 race wins. He retired from F1 racing in 2012 after an unmatched seven world titles.
The Mercedes team, for which Schumacher raced in the last three years of his career, posted on Twitter: "Encouraging news on Michael's condition this morning. We couldn't ask for a better start to the week."
That was echoed by former world champion and Schumacher rival Fernando Alonso, who tweeted: "Good start of the week with the news of Michael! So happy this is going in the good direction!"
Germany midfielder Lukas Podolski also took to Twitter hours before his team's opening World Cup match, writing: "What a great news!!! Get well soon Schumi!!! I'm so glad and happy when I just heard it!!"
Angela Charlton in Paris and AP Medical Writer Maria Cheng in London contributed to this report.