Can a sporting facility's claim that I assumed the risk of injury when I chose to play on their grounds be a valid defense to my claim that their negligence caused my personal injuries?

The short answer to this is maybe. As set forth in our blog on this subject, New York's courts have held that although in many cases a plaintiff's case will be dismissed if he undertook the sporting activity knowing that he was risking injury, there are cases, such as where the defective condition is hidden from the public, but was either known or should have been known by the operator of the sporting facility, where the courts have allowed these claims to be tried by a jury.