Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Although other studies have also demonstrated these findings (2,9,21), these results are contrary to more recent reports published from other institutions and joint registries which suggest functional outcome is inferior to that following primary TKR, with suggestion that it is actually similar to that following revision of a primary TKR at six-months (3,15,19,24).
Category: