 Trabecular MetalTM is a relatively new technology and its use in tibial knee arthroplasty components represents a significant departure from conventional total knee arthroplasties. TM has a high co-efficient of friction and high affinity for bone ingrowth Bobyn et al. 1999a, Bobyn et al. 1999b, Hacking et al. 2000, subsequently, the aims of incorporating TMM into tibial prostheses is to improve initial fixation of the tibial prosthesis at the time of implantation and to improve long term prosthesis survival by facilitating bone ingrowth. Such advantages remain, however, theoretical, and have yet to be demonstrated in vivo for total knee arthroplasty. With conventional study techniques, a definitive answer to the effect of the prosthetic design on fixation of the tibial component would require a large number of patients and approximately 10 years of follow-up Ryd 1992, Ryd et al. 1995. RSA provides a means of accurately assessing the tibial component fixation, both immediate and long term, on a relatively small number of patients within two years of the onset of the study. It is critical at this stage to determine the long-term effect of this design concept on component fixation so that any deleterious effects can be addressed and any advantageous effects can be disseminated to the orthopaedic community. 