"After France I had about another month of rehab to try to put things right again, but my knee was still giving me problems so I had another operation and I've now had the joint cleaned out and tidied up the cartilage again. There was a lot of scar tissue from the previous operation which could have caused some of the pain," Ferris told www.UlsterRugby.ie.
The 22-year-old, who has four Ireland caps to his name, has not played for Ulster since last the full 80 minutes against Glasgow Warriors in early November but has been encouraged by the rehabilitation work he has been able to get through.
"My rehab's been going really well, it's been really positive. It has been hard work, sometimes I think people seem to think that when you are off you get an easy time of it, but you don't.
"Everyone (in the Ulster squad bar the internationals) has had a week off this week but I've been in with a few injured players working with Phil (Morrow, the fitness coach). My knee has come along really well, GG (physio Gareth Robinson) and Phil have been tremendous and their input is really paying off," he admitted.
"I hope to be back training with the rest of the squad by January 31. I've been on the pitch with Phil a lot this week so should be ready to join the rest of the squad next week."
Part of Ferris' rehab work has included sled walking. "I've been doing it for my endurance - it's not nice especially when you've had three or four weeks of rain and you're dragging a 100 kilo sled through puddles for about a mile all together!"
He is aiming to be fully fit in time for Ulster's league clash with the Dragons on February 15, adding that "I've reached my goals so far so I'm feeling confident."
A member of the IRFU PricewaterhouseCoopers High Performance Select Group for 2008, Ferris was encouraged by what he saw in Ulster's Heineken Cup defeat to Gloucester last week and also by the attitude and ideas of the province's newly-appointed coach Matt Williams.
He said: "Matt's coming back soon (from Australia) and I'm really looking forward to working with him. My impression of him in the few days that he was here was very good but more than anything I'm looking forward to getting back on the pitch playing for Ulster and playing for the jersey again."