Henry was stretchered off during last Saturday's defeat at Leeds following a heavy challenge by Stephen Warnock.
Although he managed to return to the pitch for the final five minutes of injury time, a scan has since confirmed ligament damage which will bring a premature end to his campaign.
"Further to a scan result, we can confirm that James has ruptured his left knee's lateral ligament," Lions physio Bobby Bacic told the club's official website.
"James will see a specialist on Monday but he will now miss the remainder of the season."
- Sports & Recreation