Steenkamp broke a bone in his right hand in the Springboks' penultimate Tri-Nations game against Australia in Perth in August but was expected to return at the end of the Currie Cup competition in October.
But, two months later, the burly prop is still struggling with the injury as the bone has failed to fully reattach and he will undergo a scan later this week.
"We are a bit worried about it," Bulls doctor Tommy Smook said.
"He is very positive at this stage but if it hasn't reattached itself, it could mean a long lay-off."
Steenkamp's injury will be a major blow to the Springboks as well as he is seen as the natural successor to veteran Os du Randt at loosehead.
The Bulls open their Super 14 campaign against the Cheetahs on February 10.