Which joint allows for rotation of the arm?

The ball and socket joint is essential for allowing a wide range of movement, including rotation. This joint features a spherical end of one bone fitting into a cup-shaped socket of another bone. In the context of the arm, the shoulder joint (a ball and socket joint) permits not only the lifting and lowering of the arm but also rotational movements. This ability to rotate the arm around its axis provides significant flexibility and range of motion compared to other types of joints.

Looking at the other options, the hinge joint primarily allows movement in one direction, such as flexion and extension, and is not designed for rotational movement. The pivot joint, while it does allow for some degree of rotation, is more specialized and is exemplified by the joint between the first and second cervical vertebrae, rather than in the arm itself. The condyloid joint allows for movement in two directions (such as flexion/extension and abduction/adduction) but does not facilitate full rotation. Thus, the ball and socket joint best accommodates the rotational movement of the arm.