The 25-year-old was out for eight months after reconstructive surgery.
Lewington scored his first try since returning as Irish beat Cornish Pirates on Saturday to secure top spot in the Championship.
"It felt like a long way away when the injury first happened," Lewington told BBC Sport. "I'm delighted to be back."
The former Leicester player was in action for England Saxons against South Africa A in June when the injury forced his early withdrawal from the tour.
Having caught the eye of national selectors during a tough Premiership campaign for London Irish last season, the club's director of rugby Nick Kennedy feels Lewington is more than capable of international recognition again.
"We've thrown him back into some of our biggest games this season and he's performed for us," Kennedy said.
"He's been getting better each game, he's a lethal finisher and definitely one I feel Eddie Jones should be taking a look at."
A long-term lay-off was difficult for Lewington, who is now hoping to secure an immediate top-flight return for Championship leaders Irish.
"The first few months (of recovery), you're borderline not really a rugby player," Lewington said. "Everything you're doing is not really to do with rugby, it's just about getting your body functional.
"But to be back now with us approaching the season run-in is great."
London Irish and England Saxons winger Alex Lewington has admitted he had some difficult days early in his recovery from a serious knee ligament injury.