Order, Supreme Court, New York County (Leland DeGrasse, J.), entered June 13, 2002, which, to the extent appealed from, denied third-party defendants’ motion for summary judgment dismissing the third-party complaint, unanimously affirmed, without costs.

Summary judgment dismissing the third-party complaint was properly denied in view of triable issues of fact (see Zuckerman v City of New York, 49 NY2d 557, 562) as to whether plaintiffs injury was in some measure attributable to the condition of the stairs in the third-party defendants’ home. The affidavit of third-party plaintiffs expert raises a triable issue as to whether there was a defective riser in third-party defendants’ staircase that caused plaintiff to fall down the staircase. While third-party defendants question the credibility of third-party plaintiffs expert, such credibility issues are properly reserved for the trier of fact (see Alvarez v New York City Hous. Auth., 295 AD2d 225). Concur — Mazzarelli, J.P., Rosenberger, Rubin and Gonzalez, JJ.