AEMCA Practice Exam

Which of the following joints is an example of a saddle joint?

1. Shoulder joint

2. Elbow joint

3. Thumb joint

4. Knee joint

The correct answer is: Thumb joint

The thumb joint, specifically the carpometacarpal joint of the thumb, is indeed a prime example of a saddle joint. Saddle joints are characterized by their unique morphology that allows movement in two different planes, enabling greater flexibility and range of motion compared to other types of joints such as hinge or ball-and-socket joints. In the case of the thumb, the opposing surfaces of the bones are shaped like a saddle, allowing the thumb to move back and forth and side to side, which is crucial for gripping and pinching actions. This distinctive movement capability is what sets the saddle joint apart, affirming that the thumb's anatomy supports this classification. Other joints, like the shoulder joint, elbow joint, and knee joint, do not exhibit this saddle-shaped structure nor the same range and type of movement inherent to saddle joints. The shoulder joint is a ball-and-socket joint, the elbow is primarily a hinge joint, and the knee, while somewhat complex, generally functions in a manner more akin to a hinge joint with some rotational capability. Thus, the thumb joint stands out as a quintessential example of a saddle joint due to its specific design and functional attributes.