The Spurs & England international winger sustained a groin injury in December which had seemed to have healed but this week scans have revealed that Lennon had sustained further tears to the groin whist training.
"He is seeing a specialist abroad and hopefully we can get somebody who can get to the bottom of the problem," Redknapp has said.
"It's shame for him and it's a shame for us. We all miss him.
"We just hope we get some good news from Aaron. He is a fantastic player."