The Ibrox side's top scorer has been contending with the knock since damaging the joint in last month's 1-0 win over Queen's Park at Hampden. McCulloch sat out the trip to Annan on January 2 but returned to the team for Saturday's 1-1 home draw with Elgin City.
Despite battling through the 90 minutes, the 34-year-old former Scotland international was far from his best and admits he may have to take another rest from top-team duties while it heals.
McCulloch - who has 22 goals already this season - told his club's official website: "I was struggling at the Queen's Park game at Hampden with my ankle. It was really sore and I was trying to protect it as much as I could.
"I then missed the midweek game at Annan and in the game on Saturday I could feel it a little bit when I was running. It's just something I'll need to have a look at and I know I need to do what is best for the team. If I'm not giving the side anything because of my ankle, it's up to me to suggest taking me out and we'll see how things go this week."
Meanwhile, Rangers have confirmed Ross Perry is to see a specialist after sustaining a broken nose in the Elgin match.
The 22-year-old defender suffered the break in a clash of heads with Elgin striker Stuart Leslie 15 minutes from the end of Saturday's Irn-Bru Third Division fixture.
Ibrox medics have ruled out any damage to Perry's cheekbone but a trip to the nose expert is required before they can accurately asses how long he will be sidelined for.
And Mathew Ryan, the Central Coast Mariners goalkeeper, has also been forced to "indefinitely postpone" his planned trial stint with Ally McCoist's team after picking up a shoulder injury in Sunday's 2-0 win over Western Sydney Wanderers.
The knock is described as "minor" by the A-League club and he is expected to be back in action in time for this Saturday's meeting with Melbourne Victory. However, the club's website claimed that "both clubs have agreed that it is in Ryan's best interests to remain in Australia under the care of the Mariners' medical department for the foreseeable future".