The 27-year-old, who was the Wallabies' starting eighthman in their 2003 World Cup final defeat to England, successfully completed a full-contact session in Sydney on Tuesday and is now available for selection ahead of their opening match against Japan on September 8.
But the experienced Lyons admits that he feared missing his second World Cup campaign as he battled to overcome the condition.
"(I am) very relieved," he said. "It was a bit touch and go there a couple of weeks ago but it improved very dramatically and I feel fine now.
"Everything's pretty close to 100% now, we had a full contact training session this morning and everything was fine.
"(It was the) first full-on 100% contact I've done and we always knew it was going to be no worries but it was just good to actually do it."
Lyons must continue a strict regime throughout the tournament, which includes up to three blood-thinning-injections per day.
Once in France Lyons will face a formidable battle of a different kind as he attempts to unseat incumbent Wycliff Palu and reclaim his World Cup starting spot.
"Obviously there's a lot of competition in the number eight spot but I'll just wait for my opportunity and once I do get an opportunity I'm pretty confident that I can do a good job and cement the starting spot," added Lyons.
When asked about World Cup opponents Wales' victory over Argentina, Lyons said: "Wales are a team that have been probably like us in some ways, a little bit up and down the last couple of years.
"But I think having a number of games at home during the World Cup could really get them off to a good start and I think it'll be a very tough game for us, the second game of the tournament in Cardiff."
Lyons said he expects a number of northern hemisphere teams to challenge at the business end of the tournament. Â
"England has shown, like a lot of teams, some good form mixed in with a bit more average form but they'll be hard to beat.
"Ireland, as they showed when we played them in the November Test last year, when they get their best 15 on the paddock, they're a really top nation and France at home will be one of the favourites," concluded Lyons.