Hinge (ginglymus) joints are uniaxial joints that permit flexion and extension; which example illustrates this type?

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

Answer: (A)

Hinge joints move mainly in one plane around a single axis, allowing flexion and extension. A classic example is the elbow joint (humeroulnar joint), where the rounded surface of the humerus fits into the trough-shaped ulna to permit bending and straightening like a door hinge. This setup restricts motion to that sagittal plane, with no significant rotation or side-to-side movement. Interphalangeal joints behave similarly, serving as other good illustrations.

In contrast, pivot joints rotate around a single axis but primarily enable rotation rather than flexion/extension (think atlas–axis). Saddle joints are capable of two directions of movement (biaxial) and allow more than just bending and straightening, while plane joints glide with limited, mostly non-axial movements.