Ladders and scaffolds expert witnesses at Technology Associates write on stepladder instability:
According to Consumer Product Safety Commission (CPSC) accident estimates, tens of thousands of stepladder accidents requiring emergency room treatment occurred annually in the United States. Approximately 85-90% of these accidents involve the user falling from the ladder and 8-9% of these injuries are serious enough to require that the victim be admitted to a hospital. In addition to posing a severe health concern, these accidents have significant loss-of-wages and high medical expense implications.
Having investigated numerous stepladder falls over the years, we have found it very common to learn that ladder accident victims are unaware of the cause of their falls and it is typical for them to respond to questions regarding causation with answers such as: “The ladder just gave way”, or “It was sudden, I don’t know what happened”, or equivalent statements. One possible cause of such accidents is associated with use of the common four legged A-shaped stepladder, which can easily be accidentally positioned such that only three of its legs are contacting the ground. This situation can also go unperceived until it is too late to avoid an accident.