To be respectful when visiting the historic churches in Europe, visitors are advised that they need to be dressed properly. That means wearing long pants, not shorts, and having your shoulders covered – no sleeveless tops.
At the Basilica of Saint Peter in the Vatican City in Italy they have even higher standards. According to the signage outside of the church, loose body parts are not permitted.
If that shoulder implant or artificial leg have the potential to come loose and fall off, you are not allowed to enter.