Which class of synovial joints allows rotation around three axes?

• A. Non-axial (gliding joints)
• B. Uniaxial (hinge and pivot)
• C. Biaxial (condylar and saddle)
• D. Triaxial (ball and socket)

Answer: (D)

Movement is described by how many axes of rotation a synovial joint permits, i.e., its degrees of freedom. Joints that rotate around three axes are triaxial or multiaxial. Ball-and-socket joints are the classic example, such as the shoulder and hip, and they allow motion in three planes with rotation around three axes. This enables flexion-extension, abduction-adduction, and internal-external rotation, giving a wide range of movement and circumduction. In contrast, non-axial joints glide with no rotation, uniaxial joints move around one axis (like hinge or pivot), and biaxial joints move around two axes (like condylar and saddle).