Saddle joint is a biaxial joint for flexion, extension, abduction, adduction, and circumduction, such as the base of the thumb. Which option identifies this type?

• A. Hinge (ginglymus) joint
• B. Pivot (trochoid) joint
• C. Saddle joint
• D. Plane (gliding) joint

Answer: (C)

Saddle joints are designed for movement in two axes, allowing flexion and extension as well as abduction and adduction, with circumduction possible as the result of combining those motions. The base of the thumb’s carpometacarpal joint is the classic example, where the articular surfaces resemble a saddle and fit together to enable this broader range of motion. That description fits the saddle joint best.

Other joint types restrict movement in different ways: hinge joints are uniaxial, mainly flexion and extension; pivot joints permit rotation around a single axis; plane joints mainly allow gliding with limited directions. These characteristics don’t provide the two-axis movement and circumduction seen in a saddle joint.