Well, in an ideal world, a prosthetic joint component would carry stress and distribute it to the underlying bone in a manner identical to the original bone. Alas, this does not happen in real life. Prosthetic components react to stresses a lot differently than the original bone that they replaced, and tend to distribute it to the remaining bone much differently. For example, in a hip prosthesis, much of the load applied to the femoral component tends to be transmitted to the bone near its distal tip. The bone near the proximal part of the component tends to have less force transmitted through to it.
Bone loss occurs here.
Since one can get quite a bit of stress shielding around a prosthesis, it's no mystery why one sees progressive bone loss around prosthetic components over the years on follow-up radiographs. The concept of stress shielding helps to explain the usual life course of a joint prosthesis. A hip prosthesis, for example, may last for 5 - 10 years before sufficient stress shielding occurs that the prosthesis loosens enough to be symptomatic. The loose prosthesis is then removed by the orthopedist, and a new one is put in. However, the native bone around the original femoral component now generally has substantially diminished bone stock.