Skin samples are taken bilaterally from the distal anterior thigh prior to disinfection to assess normal bacterial quantity. Following disinfection and complete evaporation of any alcohols, baseline samples will be taken from both knees in order to document equal bacterial quantity prior to draping. After the duration of the intervention (75 minutes), post-intervention samples will be taken from the no-drape knee, followed by opening of the Ioban draping over he sampling areas using sterile a scissor and surgical forceps. The skin is then sampled. Samples will be taken from a suprapatellar skin area, corresponding to the skin covering the borders of the quadriceps femoris muscle tendon and from an infrapatellar area of skin covering borders of the patellar ligament. These areas correspond to the skin bordering the incision line of the medial para-patellar approach commonly used in TKA surgery. The precise area for sampling in these regions is chosen at sampling time to enable minimal leakage between the skin and the sampling cylinder.