What Happens When You Crack Your Knuckles

By Ehren Allen, DPT/Certified Orthopedic Manual Therapist

Understanding What Happens When You Crack Your Knuckles

Do you often crack your knuckles and wonder what exactly is happening inside your joints? Is it bad to pop your knuckles? You’re not alone. The mystery behind knuckle cracking has captivated many. This article will delve into the science of what happens when you crack your knuckles, dispel common myths such as “is knuckle cracking bad”, and provide guidance for maintaining healthy joints.  Explore the science behind what happens when you crack your knuckles on joionline.net.  At JOI, we are here to help answer questions about your orthopedic well-being.

Cracking Your Knuckles

What happens when you crack your knuckles? It may be background noise, or it may be like nails on a chalkboard, but there is nothing quite like hearing the sound of someone cracking their knuckles.  As a child, I was a habitual knuckle cracker.  My parents constantly fussed at me about it.  “It’s not good for you” and “you’ll get arthritis,” they would say.  But I couldn’t resist.  It felt good.  I grew up thinking this was a bad habit.  But I never really understood what actually happens when you crack your knuckles.

Image of a happy woman cracking her knuckles at a desk. JOI Rehab

Happy woman cracking her knuckles.

Is It Harmful to Crack Your Knuckles? The Science Unveiled

What causes that distinctive cracking sound when you flex your knuckles? Is it safe to crack your knuckles? The noise is not due to your bones rubbing against one another, but the formation and bursting of gas bubbles within the synovial fluid that lubricates your joints.

When force is applied to a joint during the act of knuckle cracking, the space between the bones increases. This sudden expansion results in a drop in pressure within the synovial fluid, causing dissolved gases like carbon dioxide and nitrogen to form tiny bubbles. The cracking sound is produced when these bubbles collapse.

There’s no conclusive evidence to suggest that knuckle cracking causes joint damage or arthritis. However, rigorous or excessive cracking could potentially lead to temporary swelling or reduced grip strength. So, is cracking your knuckles bad for you? Generally, it doesn’t cause harm, although some individuals might experience temporary discomfort or stiffness due to the stretching of surrounding ligaments or tendons. These symptoms usually subside within a few minutes.

What Are the Knuckles?

“Knuckle” is a common term to describe joints in the hands and fingers.  A common joint that people tend to crack is the Metacarpophalangeal joint or MCP.  Some people crack every joint in their fingers.

There are many joints in the hands and fingers.  The bones of those joints are connected by ligaments that allow movement.  A joint capsule also connects the joints.  The capsule is a closed space between the joint’s surfaces that contain a lubricant called synovial fluid.  The lubricant allows for smooth movement as the joint moves during activity.  It also contains nutrients to supply the surfaces of the joint.

Illustration showing the bones of the hand. JOI Rehab

Illustration of the bones of the hand

Is It Bad to Crack Your Knuckles? Debunking Misconceptions

Let’s address some common misconceptions about knuckle cracking.

Can knuckle cracking cause arthritis?

The simple answer is no. The popping sound you hear when cracking your knuckles is due to the release of gas bubbles within the synovial fluid, not the sign of any harmful activity that could lead to arthritis.

Are there long-term consequences from cracking your fingers?

While excessive or forceful knuckle cracking may cause temporary swelling or reduced grip strength, these effects usually resolve without causing permanent damage. So, is it bad cracking your knuckles? Not necessarily, but if you experience persistent pain, swelling, or other worrisome symptoms, seek professional medical advice.

Can knuckle cracking enlarge your joints?

This is a myth. The size of your joints is determined by factors like genetics and age, not by cracking your knuckles.

Does Cracking Your Knuckles Cause Arthritis?

There have been numerous studies performed to determine whether cracking your knuckles causes arthritis.  Many of the studies used ultrasound imaging and MRIs to determine the difference in joints’ health in the hand between those who crack their knuckles and those who do not.  Overwhelmingly, studies show no significant difference in the incidence of osteoarthritis between knuckle crackers and non-knuckle crackers.  So, the answer is NO, cracking your knuckles does not cause arthritis.

Click here to read more about Arthritis of the Hand.

Image of elderly hands that have arthritis in the hand bones. JOI Rehab

Arthritis of the Hands

Is Cracking Your Knuckles a Bad Habit?

Knuckle cracking is definitely a habit for many.  One reason is that it feels good.  When the bubbles are popped, there can be an immediate increase in the movement of the joint.  This is because the gas bubbles take up space.  When they release, there is more room for movement, at least temporarily.  The bubbles re-form, and the joint can be popped again soon.

But there may also be a chemical reason that it feels good.  When the joint pops, natural chemicals can be released call endorphins.  Endorphins are “feel good” chemicals in your body.  This chemical release may also be part of what makes cracking your knuckles a habit.

But is it a bad habit?  It depends on who you ask.  Cracking your knuckles can be an annoyance to others, but there is no significant evidence that it causes any harm to the joints of the hands and fingers.

Promoting Joint Health

Maintaining healthy joints is crucial for overall physical wellbeing. If you’re wondering, “Is it bad to crack your knuckles?”, you should also be considering how to look after your joints.

Healthy habits for joint care:

  • Keep moving: Regular physical activity strengthens the muscles around your joints, providing better support.
  • Maintain a balanced diet: Eating a diverse mix of nutrient-rich foods can contribute to joint health.
  • Watch your weight: Carrying excess weight can strain your joints, so maintaining a healthy weight can help protect them.

Exercises for joint flexibility:

  • Low-impact activities: Swimming, cycling, and brisk walking are gentle on your joints, yet offer cardiovascular benefits.
  • Stretching: Regular stretching can improve joint flexibility and motion range.
  • Strength training: Strengthening the muscles around your joints can provide stability and reduce injury risk.
wrist flexor stretch

Tennis Elbow Stretching

Actions to avoid:

  • Bad posture: Ensuring good posture can help avoid unnecessary joint stress.
  • Smoking: Quitting smoking can reduce joint pain and inflammation.
  • Repetitive movements: Vary your activities to prevent straining your joints.

By adopting these practices, you can promote joint health, enabling an active, pain-free lifestyle even if you regularly crack your knuckles.

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