A medical device for treating hip joint osteoarthritis in a human patient by providing at least one artificial hip joint surface is provided. The medical device is adapted to be inserted through a hole in said pelvic bone from the opposite side from said acetabulum, to be in contact with said pelvic bone, and to transfer a load from said medical device to said pelvic bone through said contact with said pelvic bone. Furthermore a medical device for treating osteoarthritis by providing a joint surface is provided, wherein said medical device comprises an artificial acetabulum surface having a largest diameter. The artificial acetabulum surface is adapted to be inserted through a hole in the pelvic bone from the opposite side from acetabulum of a human patient for providing said joint surface, the artificial acetabulum surface comprises at least one supporting member. The at least one supporting member is adapted to be in connection with the pelvic bone after insertion through said hole in the pelvic bone, and carry the load placed on caput femur from the weight of said human patient by the connection with the pelvic bone after insertion through said hole in the pelvic bone.
