He said migraines he had after the knock from Irish flanker CJ Stander left him listless and bereft of energy.
"The thinking was that the trauma and the stress of the knocks against my head triggered a constant or chronic migraine. I had a low grade migraine for, I guess, three months," Lambie said on Monday.
"I was waking up every morning with a headache, sore eyes, low energy and really not feeling up to much.
"But thankfully the doctors looked after me, I saw a few neurologists, had a few courses of medication and I've come right now.
"Everyone has cleared me and they're all happy that I'm playing again.
"There is no risk of me being more susceptible to concussion than there was before."
Lambie might not make the starting line-up, to be named on Thursday, but looks likely to play some part in the game, possibly off the bench.
- AAP