Gavin Henson's hopes of playing in this season's Six Nations tournament are over, after his knee injury was diagnosed as being more serious than first feared.

The 25-year-old centre has not started a Test for Wales since the autumn series opener against Australia four months ago, and a second scan on his knee last night revealed a strained posterior cruciate ligament, meaning a lay-off of between three and four weeks.

The 20 times-capped Ospreys star has not been part of Wales coach Gareth Jenkins' plans during the current Six Nations campaign, despite his team losing successive games against Ireland, Scotland and France.

"He has a ligament injury at the back of his knee," said Ospreys director of rugby Kevin Hopkins. "It doesn't need surgery, but he must rest." Henson now faces a race to be fit for the Ospreys' EDF Energy Cup semi-final clash against Cardiff Blues at the Millennium Stadium on March 24.