A shoulder joint is provided. The shoulder joint includes a main support, a fold-out arm, first and second carriages arranged on the main support, and a first coupling that is operable to couple the first and second carriages together. The fold-out arm is attached by a pin to the second carriage, and the first carriage is connected to the fold-out arm in such a way that when the first and second carriages are operable to move towards each other, the fold-out arm is folded out by pivoting around the pin. The first coupling is operable to couple the first and second carriages together when the fold-out arm is folded out, and the first and second carriages are operable to move jointly in at least one direction when coupled together.