The present invention relates to a method and a device for alleviating and/or preventing conditions relating to damaged joints involving articulating surfaces, a prosthetic device for insertion into a joint cavity of a joint of a vertebrate, such as a human, said device consisting of a biocompatible material comprising at least a first polymeric component and a second polymeric component, wherein the chain length of the first polymeric component is longer than the chain length of the second polymeric component, the polymeric components in particular being polyethylene, polypropylene and/or polyvinylpyrrolidone. A further aspect of the invention relates to a method for introducing the prosthetic device into a joint, such as a method comprising locking the device to an intro-articular component, thereby fixing or retaining the device in the joint cavity in a manner which is substantially non-invasive with respect to cartilage and bone natively present in the joint cavity. Also the invention relates to an instrument for inserting a prosthetic device according to the invention, comprising means for deforming the prosthetic device into a reduced volume or a slender shape and means for grasping the intra-articular component to which the device is capable of interlocking.