Purpose: Metal ion release by orthopaedic implants may cause local and systemic effects and induce hypersensitivity reactions. Coated implants have been developed to prevent or reduce these effects. This study was initiated to investigate the safety of a novel coating for total knee arthroplasty (TKA) implants. Methods: A total of 120 patients undergoing primary TKA with no history of hypersensitivity and no other metal implant were randomised to receive either a coated or uncoated implant. Chromium (Cr), cobalt (Co), molybdenum (Mb) and nickel (Ni) hypersensitivity patch testing and plasma ion concentrations were evaluated pre-operatively and one year post-operatively. Results: At the one year follow-up both groups demonstrated significant improvement in knee function and quality of life. One new weakly positive reaction to Co in the TKA group with coated implant and two doubtful skin reactions to Ni (one in each group) were noted. Even with sensitisation to implant materials no skin reactions were observed. Plasma metal ion concentrations did not increase and were not elevated at the one year follow-up in either group. Conclusions: Sensitisation after TKA was rare and had no influence on clinical results. TKA with coated implant and standard TKA demonstrated no plasma metal ion elevation.