The former Tottenham player has suffered an anterior cruciate ligament injury, which will see him out of action for a prolonged period of time, per the club's official Twitter feed:
A report on the QPR website suggests that the player will be sidelined for between six and nine months with the club's Head of Medical Services, Dr. Peter Florida, saying:
JJ has completely ruptured his Anterior Cruciate Ligament in his right knee. We'll be taking him to see a specialist later this week to decide the next course of action. At this stage it would appear he'll require a full repair, which is likely to keep him out for between 6-9 months.
It is a recurring theme for the Englishman, who has suffered more than his fair share of long-term injuries in his career, as WhoScored.com's Brad Pinard notes:
With QPR looking to gain promotion back into the Premier League via the playoffs, Jenas' injury will be a major blow, as noted by Sky Sports' James Marshment:
He has made 15 appearances as a starter and 11 as a substitute for QPR this season, scoring two goals and providing two assists, per WhoScored.com.
Harry Redknapp's side have one game remaining in the Championship, in which they will finish fourth, and will likely take on either Reading, Wigan or Brighton in the playoff semi-final.
If they can make it through that semi-final, the first leg of which will be played on May 8, they will likely take on Derby at Wembley to see who will fill the last promotion spot.
However, Jenas has no chance of featuring for some time, and his future at QPR may now be in danger as he is out of contract in the summer, per Sky Sports.