What is the main characteristic of flexion?

The main characteristic of flexion is that it decreases the angle of the joint. When a joint undergoes flexion, the two segments of the limb decrease the angle between them. For example, when you bend your elbow to bring your hand towards your shoulder, you are performing flexion at the elbow joint. This action effectively reduces the angle from a straight position towards a more acute angle, illustrating the defining feature of flexion in joint movements.

In contrast, the other options refer to different types of movements. Increasing the angle of the joint corresponds to extension rather than flexion. Moving a limb away from the midline is known as abduction, and turning the foot outward describes external rotation, neither of which relates to the flexion movement. Understanding these distinctions is crucial in fields like anatomy and physical therapy, where precise terminology defines movement mechanics.