A surgically implantable breast prosthesis includes an outer shell defining a first interior volume filled with a liquid filler, and an inflatable inner bladder disposed in the first interior volume and defining a second interior volume. The inflatable inner bladder is selectively fillable with the liquid filler via a valve assembly accessible from an exterior of the outer shell. The valve assembly is substantially non-palpable and includes identifying structure that is discoverable using an external device. The valve assembly includes an injection port that provides access to the inflatable inner bladder such that a size of the inflatable inner bladder is adjustable.