The formation and development of wear is now widely accepted as one of the major concerns in the long-term survivorship of contemporary knee prostheses in vivo. This review examines the role of surface topography, third-body debris, load, contact mechanics and material quality in the wear process. Some of the kinematic and physiological issues that need to be modelled in the development of wear testing regimes for evaluation of material combinations and geometrical combinations in total knee implant designs are considered. Wear testing procedures and some of the results from wear tests are discussed and the need to consider the impact of rolling and sliding in the study of wear in total knee components is highlighted. The dominant wear mechanisms that occur in vivo are identified and the role of these mechanisms is currently being examined experimentally at the University of Limerick wear testing machine.