The left back has been out of action for three months after dislocating his shoulder on international duty with Scotland back in October.
Robertson underwent surgery on the issue, prolonging his absence. However, he has stepped up his recovery since the turn of the year and has been pictured re-joining his teammates in training following the winter break.
Speaking in his pre-match press conference ahead of the Carabao Cup semi-final second leg away against Fulham, Lijnders revealed the news that Robertson is fit again to take part in first-team duties and will be part of the squad to travel to London.
Lijnders told reporters: "Let's start with Robbo because he trained yesterday with the team. It's now 13 weeks, he had his meeting with the surgeon to make sure that everything is right to go into full contact – it's clear. So he did a lot of work and really good rehab throughout the last period, so he's fit in terms of sports science. Now he has to get fit with proper team training.
"So that's a big, big advantage to have him back. We were waiting for a long time – he's one of our captains. I just met him in the canteen and he said, 'Pep, I have my tracksuit with me!' So he's pushing himself into the squad, so that's good. He will travel [to Fulham].
Meanwhile, Lijnders gave positive updates on the Liverpool's other injured stars, first revealing that Curtis Jones sustained no issue, despite a precautionary substitution in the Reds' win over Bournemouth at the weekend.
He said: "When you play more games and when you are constantly in the team since a long, long time, you get also some small niggles. He already reported during the week some tension in his hamstring tendon. But yesterday [there were] no issues, so he was clear. And during the game it was more precautionary [because] we go 3-0 up and the guy, even if he's young, he acts like a senior, so he made the right decision."
He continued: "Trent is progressing well through his rehab, working hard – how he is as a guy, knowing how important the next weeks are. But he will back in the end of the week for team training, so hopefully he will be available for the FA Cup.
"Dom trained yesterday with us, just one small-sided game, one-touch game, but played good, felt good, did some extra work with the sports science team. He is ready but tomorrow comes too early for him, so he will be ready for the weekend if nothing goes wrong.
"Kostas is now four weeks after surgery, so he needs probably two more weeks because we need to make sure that the bone is strong and the bone is healed before he goes into first-team training."