How does a bicondylar joint differ from a hinge joint?

A bicondylar joint differs from a hinge joint primarily in its anatomical structure and the range of motion it permits.

• Anatomical Structure: A bicondylar joint is defined by two distinct pairs of mating surfaces on the same bones that articulate together. In contrast, a hinge joint (or ginglymus) is a modified sellar joint where each mating surface is ovoid on its sides.
• Range of Motion: Hinge joints are restricted to movement in a single plane, functioning like the hinge of a door to allow for a backward-forward swing, often accompanied by a slight spin. Bicondylar joints are more complex, allowing for two types of movement: one is always a swing, while the second can be either another swing or a spin. For example, while the tibiofemoral joint primarily facilitates flexion and extension, it also permits active rotation of the leg when the knee is bent.123

Both are classified as synovial joints, but their distinct articular shapes dictate their functional capabilities.34