The mean surviving CFU/cm2 are then compared. Comparison will be performed within the same knee and between knees in the same patient. Samples from one knee are compared at different sampling times (baseline, 10 minutes after disinfection and 75 minutes after start of simulated surgery). Analysis between knees will be performed between the drape group and the non-drape group at all sampling times. Finally, a mean bacterial regrowth will be calculated as a variable representing the increase in bacterial density between sampling performed before and after the use of Ioban drape. The regrowth of bacteria in the two settings are then compared.