Which of the following factors primarily affects the range of motion in joints?

Joint structure is a crucial determinant of the range of motion in joints because it encompasses the anatomical configuration and the relationship of bones, ligaments, and cartilage that make up the joint. Each type of joint (such as hinge, ball-and-socket, or pivot) inherently allows for different movements and degrees of motion. For example, ball-and-socket joints like the hip and shoulder provide a wide range of motion in multiple planes, while hinge joints like the knee allow for motion primarily in one direction.

Variability in joint structure—such as the shape and depth of bony surfaces, the tightness of ligaments, and the integrity of articular cartilage—can significantly influence both passive and active range of motion. Moreover, factors like congenital conditions, injuries, arthritis, and previous surgeries can alter this structure and thus limit movement. Understanding the importance of joint structure helps in assessing and treating conditions related to mobility and flexibility in various therapeutic settings.