James Morrison could be back playing before the end of the season after club doctors revealed his injury was not as bad as first feared.
The Scotland international was carried off in West Brom's 3-1 defeat at Newcastle and was expected to be out until the summer.
But scans showed that the damage was to his medial and not his cruciate ligament and means the medical staff could give him the green light to start training.
"We have had positive news on James," Albion's head of medical services, Mark Gillett, told the club's official website.
"We came to the conclusion on Sunday that it would more likely be a medial ligament issue, rather than a cruciate one, but you cannot be 100 per cent sure until the swelling has receded and you get the injury scanned.
"The outcome is that his rehab period will be more a case of a few weeks than months and, if it all goes to plan, he should be able to play again this season."