It's the goal celebration every youngster dreams of.You smash one into the net and you sprint off to the corner-flag and give it a massive knee-slide in front of your adoring fans.It looks cool, it's emphatic and most of all, it's easy.Or at least it should be.Enter Arjen Robben, who scored both goals for Bayern Munich in their 2-0 win over Eintracht Braunschweig today.You'd think a man of his goalscoring pedigree - over 150 strikes for club and country, including the winner in the Champions League final - would have no problem executing a knee-slide.But you'd be wrong. The Dutchman fell came a cropper as his red thermal tights - apparently velcro-coated - produced such friction on landing that Robben was catapulted through the air before landing with an embarrassing bump.Just look at the damage done to the poor man's knees - Mrs Robben will be reaching for the Dettol tonight.Maybe stick to a handshake next time, eh?Here's a quick reminder of how it should be done.(uk.eurosport.yahoo.com)ANN.Az