'Duncan is walking fine, but is experiencing some discomfort when he changes direction. It's potentially ligament damage which, if confirmed, could see him ruled out for up to six weeks,' said a Neath spokesman.
The 24-years-old Jones won the first of his three caps as a replacement against Australia two years ago and followed by coming off the bench in the following match against Ireland in February 2002.
His third appearance was again as a replacement, against France at Cardiff two weeks later - the first match with Hansen as Wales coach.
Given the current problems in the Wales front row, Jones would have been eyeing a late call-up to Hansen's Six Nations squad.
Once fit, he must focus on producing displays that could put him in the frame for selection for Wales' World Cup warm-up games.
Wales head down under for matches against Australia in Sydney (June 14), and then they face the All Blacks in Hamilton, Waikato one week later.