Abstract. Introduction. There are a wide variety of implant brands and types of knee replacement available to surgeons. With time, the options available within many implant brand portfolios has grown, with alternative tibial or femoral components, tibial insert materials or shapes and patella resurfacings. Aim. To investigate the effect of the expansion of implant brand portfolios, and to establish the potential numbers of compatible implant construct combinations. Methods. Hypothetical implant brand portfolios were proposed, and the number of compatible implant construct combinations was calculated. Results. A simple knee portfolio with cemented cruciate-retaining (CR) and posterior-stabilised (PS) components, with and without a patella has 4 combinations. If there are two options available for each, the numbers double for each option, resulting in 32 combinations. The effect of adding a third option multiplies the number by 1.3. Introducing compatible uncemented options, with the effect of hybrids multiplies the number by 4. An implant portfolio with two femoral components (both in CR and PS), with two insert options and a patella, all in cemented and uncemented versions leads to 192 possible compatible implant construct combinations. There are implant brands available with many more than two options available for use. Conclusion. This study demonstrates that the addition of multiple variants within a knee brand portfolio leads to a large number (many hundreds) of compatible implant construct combinations. Revision rates of implant combinations are not currently reviewed at this level of granularity, leading to the risk of implant camouflage