Fig. 1

Radiological assessment quality (RAQ) criteria for assessing alignment. The evaluation was done using a five yes/no question checklist that was devised for this review. A sensitivity analysis was performed to determine if the quality of the radiological methods was an important factor in the outcome. The rationale for each set of questions was as follows: The suitability of the imaging modality used: Overall limb alignment is better assessed on a whole leg radiograph compared to a short film radiographs (Moreland 1988) and Short film x-rays are used for the assessment of component’s anatomical alignment (Morgan et al. 2008). The timing of the imaging: Malalignment on images acquired several years following surgery may be secondary to implant subsidence/migration (Morgan et al. 2008). The patient’s weight bearing status at the time of imaging: the relationship between the bony and soft tissue parts of the knee joint is most visible during stressing manoeuvre such as weight bearing (Nicoll and Rowley 2010). Indication of standardisation when acquiring the images: Non-standardised protocols for acquiring images can result in inconsistent magnification and rotation, introducing a source of bias (Parratte et al. 2010; Registry 2013). Evidence of rater reliability when assessing the images for alignment: To ensure consistency (Parratte et al. 2010; Registry 2013)