Response to commentary on 'Instruments to assess appropriateness of hip and knee arthroplasty: a systematic review'

We appreciate the opportunity to respond to the comments from Riddle and Ghomrawi on our systematic review titled 'Instruments to assess appropriateness of hip and knee arthroplasty: a systematic review'. This response will address the three comments raised by the authors: 1) conceptualisation of appropriateness; 2) the appropriateness framework used to assess instruments; and 3) inclusion of appropriateness criteria specific to patient perspectives (e.g., shared decision making, expectations). Although the concept of appropriateness has evolved over the last 20 years,1 Riddle and Ghomrawi grounded their concerns over our systematic review based only on the RAND appropriateness definition.2 They suggested that the RAND methodology is the only valid method for developing appropriateness criteria, but it is one of many,3 as there is no As pointed out by Riddle and Ghomrawi, only 8 of the 55 instruments included in our systematic review were developed following the RAND methodology (15%), accounting for 24.6% (n = 30) of the total number of included studies (n = 122). The argument that only instruments developed using the RAND methodology are 'scientifically valid' would suggest that 47 instruments and 92 corresponding studies pub