Madden, underwent a pelvic scan last week, and the results have lead to the possibility that surgery may be the best way forward for the 29 year-old.
Scarlets director of rugby Gareth Jenkins said: ''Martyn's injury is long-term at the moment. There is a concern about his groin and it looks as if it possibly needs surgery. It is a big disappointment because we need his playing ability and quality on the field and in the squad.''
Madden has been a key figure in the front row for Llanelli in recent seasons, last term he scored five tries making him joint third top scorer in the Heineken Cup, and his dynamic play has won him acclaim from the Wales management.
Madden was in the frame for a place at the Rugby World Cup, but the injury to his groin forced him to withdraw from Steve Hansen's training squad earlier in the year.