The 22-year-old limped off late in Sunday's 2-1 defeat at home to Manchester United after falling awkwardly and appearing to twist his right leg. He has had the injury assessed and it requires surgery, which is likely to sideline him for at least six months.
"Martin Kelly is likely to be out of action for a significant period of time after scans revealed he suffered an ACL rupture of his right knee during the match against Manchester United on Sunday," said a statement from Liverpool. "The England international will now require ACL reconstruction."
The full-back admitted as such earlier in the day when he wrote on Twitter:
"What I can say is its not the worst injury I've had, and for sure I'll be fighting for my place next year when I'm back fitter and stronger!"
There is slightly better news concerning Sunday's other two injury worries, however. Centre-back Daniel Agger was carried off on a stretcher in the second half after a collision with team-mate Glen Johnson. Considering the Denmark international's injury record there was immediate concern but initial examinations have revealed there is no ligament damage only what the club describe as "a significant bone bruise to the left knee".
"No ligament damage was sustained but further tests will be carried out before it can be established when he will be able to return to training," Liverpool said. Forward Fabio Borini was forced off at half-time with a bruised foot and swollen right ankle and although there is no fracture he requires further investigation at the Reds' Melwood training ground.
"The club's medical staff will wait for the swelling to reduce before an MRI scan can take place tomorrow to assess any soft tissue damage and determine when he may be able to return to playing," was the club's assessment.