23 May, 09:41
The IRFU is currently inviting applications for the position of Communications and Media Officer.
The big Springbok second row had surgery today (Sunday) to repair the damage and is expected to be out for eight weeks.
Capped 26 times by South Africa, Muller has played 50 times for Ulster and has been the province's captain since August 2011.
His leadership has been instrumental in helping Ulster to an unbeaten start in both the RaboDirect PRO12 and Heineken Cup this season.
His current contract with the province runs until the summer of 2013.