Choose the factors that determine a joint’s range of motion.
Check all that apply.
A Tendons limit a joints range of motion, but muscles play a minor role.
B In many cases, joint movement is limited by the shapes of the bone surfaces.
C Bones are joined by ligaments that limit their movement.
D In many joints, pairs of muscles oppose each other and moderate the speed and range of joint motion.
The correct answer and explanation is :
The correct answers are:
B. In many cases, joint movement is limited by the shapes of the bone surfaces.
C. Bones are joined by ligaments that limit their movement.
D. In many joints, pairs of muscles oppose each other and moderate the speed and range of joint motion.
Explanation:
- Shape of the bone surfaces (B):
The structure of the bones at a joint significantly impacts the range of motion. In ball-and-socket joints, such as the shoulder and hip, the ball-shaped head of one bone fits into a cup-like cavity of the other bone. The shape and depth of these surfaces can limit how far the joint can move. For example, the shallow acetabulum in the hip limits the hip’s range of motion, while the more shallow joint surfaces in the shoulder allow for a broader range of movement. In hinge joints like the knee, the flat or slightly curved articular surfaces also restrict movement to mostly one direction. - Ligaments (C):
Ligaments are connective tissues that hold bones together at joints. They are essential in maintaining joint stability but also restrict the excessive motion that could lead to injury. For example, the ligaments of the knee, such as the anterior cruciate ligament (ACL), prevent hyperextension and stabilize the joint. If ligaments were too loose, the joint would move too freely and risk damage to both the bone and surrounding tissues. Ligaments therefore help define the limits of joint movement. - Muscle opposition (D):
Muscles around a joint control its movement, and they often work in pairs to ensure the motion occurs in a controlled and safe manner. For example, the biceps and triceps work together at the elbow joint to control the range of flexion and extension. The antagonist muscles prevent overextension or hyperflexion by counteracting the force exerted by the agonist muscles. In this way, the muscles modulate not only the speed but also the range of motion to avoid injury or excessive strain on the joint. - Tendons and muscles (A):
While tendons connect muscles to bones and allow movement, they don’t directly limit joint range of motion as stated in option A. Tendons can restrict movement if they are too tight, but it is the ligaments and the shape of the bones that primarily limit movement, not the tendons themselves. Muscles do play a critical role in controlling joint movement, but tendons are passive in terms of limiting range of motion.
Thus, B, C, and D are the factors that most directly influence a joint’s range of motion.