The 21-year-old thought he had recovered from a knee cartilage injury when Accies suffered a 5-0 drubbing in Govan.
However, it was the last match McKenna played before he underwent surgery to get to the root of the problem.
And after a long period of rehab and a place on the bench against Motherwell in Accies' previous outing, he is looking to get back into Brian Rice's side for the Ladbrokes Premiership clash versus the Light Blues.
McKenna said: "I came back pretty quickly. It was the adrenaline of the whole experience that got me through it fine.
"But knowing that I needed an operation, maybe I wasn't at 100 per cent.
"It was quite a frustrating injury because when it happened we weren't quite sure how long it was going to be, it looked quite positive at the beginning.
"We were trying to avoid an operation and I missed out for five or six weeks and tried to come back around October time.
"I was back for four weeks and I felt something wasn't quite right and kept getting set back and finally had an operation in November.
"I was unsure whether that was going to solve it but it did and I am feeling great so I am delighted the injury is behind me and I'm back in training.
"Hopefully Ibrox will go better than last time."
McKenna came through Celtic's youth academy before moving to the United States on a soccer scholarship at Duke University in 2015.
He returned to Scotland in January 2019 and joined Accies last summer after a short spell at Falkirk.
McKenna believes the experience of playing three times against Celtic and Rangers this season already can help Accies get their first points of the campaign against one of the Glasgow giants.
He said: "It could help us. We have had four or five games against the Old Firm this season and in a lot of them we have run them close, especially at home.
"At Celtic Park we took it to the last minute so I think we have performed pretty well against the Old Firm and maybe just lost that bit of steam in the last 10 minutes.
"Obviously the last time at Ibrox it went a little bit differently than recent games against the Old Firm here but hopefully we can hold them out and maybe take them all the way instead of falling at the last step."
McKenna will not read too much into Rangers' downturn in fortunes since they have returned from the winter break.
The Light Blues have fallen 12 points behind Celtic at the top of the Ladbrokes Premiership and were knocked out of the William Hill Scottish Cup by Hearts on Saturday.
He said: "We still know how good Rangers can be on their day.
"You can't really worry about them and how they turn up and their form, it is more about focusing on ourselves and making sure we are right and organised as best as we can be."