hydrogels for use in the present invention comprise a blend of pva and 0 1 to 50 more preferably 1 to 5 of a second polymer preferably pvp or copolymers of pvp and poly methyl methacrylate poly acrylamide poly acrylic acid poly acrylonitrile or poly ethylene glycol in a preferred embodiment the hydrogel comprises a blend of pva and 2 5 pvp it is believed that implantation of the prosthetic nucleus of the present invention will be useful in alleviating the pain in mammals in particular humans suffering from intervertebral disc degeneration the associating gel composed of pva and pvp is a u201c memory u201d material meaning that it can remember or regain a given geometry from its hydrated to dehydrated states this material property can be exploited by inserting the copolymer material as an implant in a dehydrated state into the nuclear cavity of the disc using arthroscopic methods known to those of skill in the art this allows for insertion of the smaller dehydrated copolymer using a clinical procedure that is minimally invasive the copolymer can be rehydrated after the insertion using physiological saline combination of a minimally invasive procedure with pain relief and potential restoration of functional joint biomechanics serves to make this new copolymer material an important advance for the surgeon and the patient four pva pvp copolymer compositions c2 c5 and pure pva c1 hydrogels were synthesized using freeze thawing techniques compositions as listed below in table 1 a 39 day degradation study was performed to establish the differences between the copolymers and pure pva five samples of each material were immersed in phosphate buffered saline pbs solutions at 7 4 ph at 37 u00b0 c for 39 days before immersion dry weights of the unswollen polymers were measured and recorded for.