Abstract: An intra-articular device comprises a membrane shaped like a cap having a peripheral geometry similar to that of a head of a bone for a joint to be restored and an open end sized to be applied over the bone proximate the head, so that the open end can be stretched over the head of the bone and held in position on the bone interposed between the head and its corresponding articular component of the joint. The membrane is made of a polyether-urethane-urea material selected to have a property of absorbing the joint's own synovial fluid so as to swell and have a viscoelastic property similar to the body's own articular hyaline cartilage. In a preferred embodiment, the membrane cap is adapted for use on a femoral bone for restoring a hip joint.

Abstract: The disclosure relates to a joint augmentation implant in the form of an elastomeric polymer cap for the ball portion of a ball and socket joint such as a hip or shoulder. The cap is adapted to swell in the presence of synovial fluid and to supplement or replace native cartilage. The disclosure also relates to methods of use of the joint augmentation implant.