Work machine arm, work implement, and work machine

A work machine comprising:

• a lower plate having a first outer surface and a first inner surface facing each other;
• an upper plate having a second outer surface and a second inner surface facing each other, the upper plate being disposed such that the second inner surface faces the first inner surface at a distance from the first inner surface;
• an arm cylinder bracket connected to the first outer surface of the lower plate;
• an arm cylinder connected to the arm cylinder bracket;
• and
• a first inner rib disposed between the lower plate and the upper plate, the first inner rib being connected to the first inner surface of the lower plate within a first connection range between the lower plate and the arm cylinder bracket in a side view,
• wherein the first inner rib has a first end and a second end located opposite to the first end, and the first inner rib is connected at the first end to the first inner surface of the lower plate and connected at the second end to the second inner surface of the upper plate, and
• wherein, in a side view, the first end of the first inner rib is connected to the first inner surface of the lower plate within an extension region in which an outer shape of the arm cylinder retracted to a maximum extent is extended in an axial direction of the arm cylinder.