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Flexion vs. Extension: What's the Difference?

By Janet White || Published on January 19, 2024
Flexion is the bending of a joint decreasing the angle between bones, while extension is straightening a joint increasing the angle.

Key Differences

Flexion involves a decrease in the angle between the bones of a joint, like bending the elbow. Extension is the opposite movement, increasing the angle as in straightening the arm.
In flexion, muscles contract to bring bones closer, commonly observed in knee bending. Extension involves muscles elongating, returning the knee to a straightened position.
Flexion is essential in daily activities, such as squatting, which reduces the hip and knee angles. Extension movements are evident when standing up from a squat, increasing these angles.
Flexion can be limited by muscle tightness or joint problems, affecting movements like bending the wrist. Extension can also be limited by similar factors, impacting the ability to fully straighten the wrist.
Flexion and extension are fundamental in exercises, with flexion seen in bicep curls and extension in leg presses, demonstrating their role in muscle strengthening.

Comparison Chart

Joint Angle Change

Decreases angle
Increases angle

Movement Example

Bending the elbow
Straightening the elbow

Muscle Action

Contracting muscles
Elongating muscles

Daily Activities

Sitting down (hip/knee flexion)
Standing up (hip/knee extension)

Exercise Example

Bicep curls (arm flexion)
Leg presses (leg extension)

Flexion and Extension Definitions


Flexion refers to reducing the angle between two body parts.
Knee flexion is necessary for walking.


Extension is the straightening of a joint.
Extension of the arm releases the thrown ball.


Flexion is the act of bending a joint.
The flexion of her fingers allowed her to grasp the object.


Extension is a movement that increases the angle of a limb at a joint.
Knee extension occurs when kicking a ball.


Flexion is a movement decreasing the angle of a limb at a joint.
Elbow flexion is used to lift weights.


Extension is the action of lengthening muscles around a joint.
Elbow extension is part of a push-up movement.


Flexion is the action of bending muscles around a joint.
Spinal flexion is common in yoga poses.


Extension increases the angle between two body parts.
Hip extension is crucial for standing up.


Flexion involves the bending of a body segment.
Neck flexion helps in looking downwards.


Extension involves straightening a body segment.
Back extension helps in maintaining posture.


The act of bending a joint or limb in the body by the action of flexors.


The act of extending or the condition of being extended
The extension of the subway into the suburbs.


The resulting condition of being bent.


What is extension?

Extension is the movement that increases the angle between body parts at a joint.

Which activities involve extension?

Extension is involved in activities like standing and reaching out.

What is flexion?

Flexion is the movement that decreases the angle between body parts at a joint.

Where is flexion commonly seen?

Flexion is common in joints like the elbows, knees, and fingers.

Is flexion always voluntary?

Flexion can be both a voluntary and involuntary movement.

Are flexion and extension opposite movements?

Yes, they are generally considered opposite movements.

What role does extension play in posture?

Extension is important for maintaining upright and proper posture.

Can extension help in back pain?

Proper extension exercises can alleviate certain types of back pain.

Can flexion be limited due to injury?

Yes, injuries can limit both flexion and extension movements.

Can flexion and extension occur in all joints?

Most joints allow flexion and extension, but the range varies.

How do flexion and extension relate to exercise?

They are key movements in many exercises for building muscle strength.

Do flexion and extension occur in the spine?

Yes, the spine is capable of both flexion and extension movements.

How is extension used in rehabilitation?

Extension exercises are often part of rehabilitation programs.

Can flexion and extension be asymmetric?

Yes, there can be asymmetry in these movements in some individuals.

Are there diseases that affect flexion and extension?

Conditions like arthritis can affect the range of both flexion and extension.

What muscles are involved in extension?

Extension typically involves muscles opposite those used in flexion.

Is flexion important for flexibility?

Yes, the ability to flex joints is a measure of flexibility.

How do flexion and extension affect balance?

They play a crucial role in maintaining and adjusting balance.

Can flexion be improved with exercise?

Yes, exercises can improve the range of flexion in joints.

Is extension limited as we age?

Aging can reduce the range of extension in some joints.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.

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