The 25-year-old underwent an operation to repair damage to his anterior cruciate ligament that he sustained against Chelsea in November.
Speaking upon his arrival to Liverpool's Melwood training complex, Lucas admitted that he was "really happy" to be back on Merseyside.
"I am really happy to be back. I've really missed my teammates and the atmosphere here, so that's why I decided to come back here to continue my rehab," he told the club's official website.
"I am still a long way away, but the knee is getting better and the rehab is going well. I have to make sure I complete a perfect rehab and be back as soon as possible.
"The next stage is to get the knee moving and in the next few weeks I'll start to walk again. Hopefully in a month's time I'll start in the gym and my programme and be able to work with weights."
The injury has ruled Lucas out for the remainder of the season.