The Wales defender had to be replaced before the break by Georgios Samaras during the 3-1 Scottish Premiership win over Hearts at Tynecastle after being injured in a challenge by defender Kevin McHattie.
Manager Lennon assessed his squad before travelling to the airport to fly out to see Milan play Torino on Saturday night, and he said: "Adam is fine. He just jarred his ankle and couldn't continue but we are hoping he will be okay for Wednesday. It is just a twist.
"James Forrest, with his sciatica problem, we are hoping he will be okay to travel and be fit and available.
"Thankfully, apart from that, we have a clean bill of health.
"The only loss, and it was a big one, was Steven Mouyokolo with an Achilles injury during the week."
Mouyokolo faces six months out of action, having suffered a complete rupture of an Achilles tendon in training.
Recent signing Teemu Pukki grabbed a debut goal as the Hoops overcame a young but hard-working Hearts side.
Kris Commons scored from the spot in the 18th minute after home midfielder Jamie Hamill was controversially penalised for handball, before Jason Holt equalised in the 56th with a deflected drive from the edge of the box.
Anthony Stokes put Celtic back in front after 65 minutes with an unstoppable volley from 12 yards before substitute Pukki, who replaced Commons, made it 3-1 five minutes from time to mark the start of his Hoops career following his move from Schalke.
Lennon was pleased with two of his other new boys, Dutch duo Derk Boerrigter and Virgil van Dijk, as he primes his team to face the Italian giants.
He said: "I thought Boerrigter was very good. He gives us pace and attacking thrust on either side of the pitch and Van Dijk, I think, is going to be a top, top player.
"He has adjusted now, he has the pace of the game and looks a really good player."
Another of Lennon's new signings, Israel midfielder Nir Biton, will join the Celtic squad in Milan.
The Celtic boss said: "Nir Biton will travel but he hasn't trained with us obviously. We will have a look at him on Tuesday and see what sort of condition he is in.
"I don't think he played any football when he was away with Israel so it might be too soon for him."