In order to sue a business or municipality for failing to address a trip-and-fall hazard, a plaintiff must first show defendant knew or should have known about the danger. If there is proof the defendant knew, that's called "actual knowledge." When the evidence shows instead the defendant should have known about it, this is called "constructive knowledge."
The latter can be established with circumstantial evidence, showing for example the condition was recurring or that it would have been discovered had defendant exercised reasonable care. If a plaintiff can't prove some form of knowledge of the danger by the defendant, he or she will have no case. It's a critical element of any premises liability lawsuit, and an experienced attorney can help determine whether there is a strong basis to prove it in your case.
It was central to the recent claim of Major v. City of Hartville, weighed by the South Carolina Supreme Court.