Medical devices firm Smith & Nephew said first quarter revenue was boosted by progress at its US knee franchise while net profit fell.During the first quarter ended 2 April 2011 revenue rose to $1.055bn from $995m the year before. Trading profit fell to $241m from $250m after it incurred higher administrative expenses. Group trading profit margin was 22.8% while net debt was reduced to $351m.Chief financial officer Adrian Hennah said, "We had a good start to the year with our US knee franchise, sports medicine repair and Negative Pressure Wound Therapy businesses all continuing their strong growth." However the London based prosthetics maker saw relatively slow growth at its replacement joints business.Geographically, S&N grew by 4% in the US, 1% in Europe and 8% in the rest of the world. S&N said orthopaedics continued its momentum from last year, outperforming the reconstruction market, driven by 10% growth in US knees. Endoscopy recorded double digit sales growth in sports medicine repair products while Advanced Wound Management delivered strong NPWT growth."We remain confident that the increased level of investment in our businesses - in particular, developing more innovative products and increasing our scale in the emerging markets - will deliver continued long term growth," it said.S&N said its outlook guidance for 2011 is unchanged.CJ