What type of joints can bend and straighten but cannot rotate?

Hinge joints are specialized synovial joints that allow movement primarily in one direction, functioning much like the hinge of a door. They enable bending and straightening movements, which is referred to as flexion and extension. This type of joint is found in areas such as the knees, elbows, and fingers. The structure of hinge joints is such that they allow movement along only one axis, limiting their functionality to bending and straightening without any rotational movement.

The other types of joints mentioned have different characteristics that allow more varied movements. For instance, gliding joints permit sliding movements but don't provide the same bending and extending action as hinge joints. Ball and socket joints allow for a wide range of motion including rotation, while pivot joints enable rotation around a single axis.