Jenny Qiu and team from the Texas Tech University and A&M University have concluded that incorporating a very viscous polymer called Alginate, can strengthen Hydrogel. This new hydrogel form is exactly like natural cartilage, and could possibly be used for replacement like Knee Cartilage.
Source: http://www.rsc.org/chemistryworld/2015/10/alginate-biocompatible-hydrogel-3d-print-knee-replacement