The issue rules him out of contention for his country's tour of South Africa this summer, with a predicted return to fitness not expected until July.
The 25-year-old is understandably eager to join up with his Cardiff Blues teammates as soon as possible but with brother Ben also on board as physio, Warburton is relaxed about making his return.
"The rehabilitation's been really good," said Warburton. "My twin brother Ben is my physiotherapist for this period which has worked out really well for me. We can be honest with each other.
"All I'm chasing really is to try and get as much pre-season in as soon as possible.
"So I think after 12 weeks I can pretty much do full conditioning with the coaches.
"I think the Blues get back together in June, so hopefully I can get a good two and a half months under my belt and go into September feeling strong and fit."