Which joints are described as the most mobile in the body, allowing motion in an infinite number of planes?

• A. Gliding joints
• B. Saddle joints
• C. Condyloid joints
• D. Ball and socket joints

Answer: (D)

Ball-and-socket joints are the most mobile in the body because their spherical head fits into a cup-shaped socket, creating a three-dimensional arrangement that allows movement around three axes. This enables flexion/extension, abduction/adduction, and rotation (along with circumduction), giving a wide range of motion in many planes. The shoulder and hip are the classic examples, providing substantial freedom for arm and leg movement. In comparison, gliding joints offer only limited sliding movements; saddle joints allow two-plane movement with less rotational freedom; and condyloid joints permit two planes of movement with some rotation, but not to the extent of ball-and-socket joints.