England hopeful Dan Ward-Smith's RBS 6 Nations campaign looks over before it has begun after the Bristol number eight suffered a serious knee injury at Franklin's Gardens.

Ward-Smith was widely tipped to win his first cap in the tournament opener against Scotland at Twickenham after two seasons of dynamic back-row performances for his club in the Guinness Premiership.

But, 15 minutes into his final game before joining up with England, he was caught in a pile-up on his own line trying to protect the ball and suffered a dislocated right kneecap that may well end his season.

The injury held up play for five minutes as Ward-Smith received oxygen from the medical team, who immobilised the knee before stretchering him off.

England coach Brian Ashton will be cursing his luck after another injury setback - and so will club boss Richard Hill at losing a player whose explosive ball-carrying presence has turned Bristol from also-rans into potential champions over the last two years.

Even without Ward-Smith, they managed to chisel out a scrappy win against the Saints - their first at Franklin's Gardens since November 2001 - by weathering an early storm and hitting back with two second-half scores.

Northampton struck when axed England wing Ben Cohen surged over on the right to add to Carlos Spencer's early penalty.

But Brian Lima snatched an opportunist's interception try after the break, Alfie To'oala added a second 10 minutes from time and Jason Strange did the rest with his two conversions.

The Saints desperately needed to pick up more than the one bonus point they snatched from this game after their chief relegation rivals Worcester held Wasps to a draw on Friday night.

Their cause was not helped by injuries in the front row - the strong suit of an experienced Bristol pack - with England hooker Steve Thompson (neck), prop Pat Barnard (head), and lock David Gerard (knee) were all ruled out.

Dylan Hartley, Soane Tonga'uiha and Damien Browne were drafted into the pack, with Robbie Kydd, Ben Cohen and Paul Diggin restored to the backline.

The visitors, meanwhile, had stiffened up their own backline, with Lima, Neil Brew and Josh Taumalolo all returning.

It was Northampton, though, who dominated the early exchanges, camping deep in Bristol territory for most of the first half and were driving for the line when Ward-Smith was knocked backwards and out of the game after 15 minutes.

Spencer nudged the Saints in front with a penalty soon after and they were a man better off when Lima was sin-binned for not rolling away from a tackle.

Bristol were made to pay in the 25th minute when Spencer opened up the game and Cohen was given the space to blast his way down the left and into the corner for his 100th try for the club.

Northampton ought to have stretched their half-time lead into a match-winning one early in the second-half, but instead surrendered the advantage.

Spencer missed with a long-range shot at goal and was directing another promising attack when Chris Budgen's hopeful pass was picked off by Lima and the Samoan raced 80 metres to score under the posts with Strange converting.

Bristol were given added impetus when Tonga'uiha was yellow-carded for pulling down a maul and the Saints had to roll with the punches until Bristol lost one of their own when lock Gareth Llewellyn followed him into the bin.

But the experienced Bristol pack built up a head of steam to work their way downfield and struck a decisive blow 10 minutes from time.

Lock Christian Short was binned for pulling down a rolling maul close to his own line before the visitors tried the tactic again and were rewarded when To'oala was driven over, Strange supplying a conversion from the left-hand touchline.

The Saints were given a glimmer of a chance after the clock had run out when replacement Sean Hohneck became the third Bristol player to be shown the yellow card but failed to take advantage when running the ball from a pair of late penalties.