Why joints pop
The medical term for joint noise is crepitus. It covers popping, cracking, clicking, snapping and grinding. Different noises have different causes, and most are harmless.
Gas bubbles and cavitation
Synovial fluid lubricates joints and contains dissolved gases. When the joint surfaces are pulled apart, pressure drops and a gas cavity forms quickly, causing a crack. Real-time MRI studies of finger joints have shown this cavity forming at the moment of the crack. Afterwards, there is a refractory period of around 20 minutes before the same joint can crack again.
Tendons and ligaments
Tendons and ligaments can snap over bony prominences as a joint moves, producing a repeated click with each movement. This is common at the knee, hip, ankle and shoulder, and is usually painless.
See snapping hip.
Grinding and cartilage
A grinding or crunching sensation can reflect roughened cartilage surfaces, particularly in the knee behind the kneecap. It becomes more common with age. Many people with noisy knees have no pain or arthritis, and noise alone is not a reason for concern.
Does cracking knuckles cause arthritis?
Studies comparing habitual knuckle crackers with non-crackers have found no increase in hand osteoarthritis. Cracking is not harmful for most people, though some find it irritating to others.
See knuckle pain.
Common popping joints
- Knees: on stairs and squatting.
- Shoulders: during overhead movements.
- Neck and back: with twisting.
- Hips: when walking or swinging the leg.
- Ankles: on getting up or rotating.
- Jaw: when opening wide or chewing.
See knee popping, shoulder popping, back cracking and jaw clicking when chewing.
Why do my joints pop so much?
- Hypermobility: more movement in the joint allows more noises.
- Stiffness after rest: joints often crack on first movement.
- Muscle imbalance or tight muscles affecting tendon tracking.
- Ageing changes in cartilage.
- Pregnancy hormones loosening ligaments.
Hypermobility and popping
People with joint hypermobility often notice frequent popping and clicking. If popping comes with pain, fatigue, frequent sprains or joints slipping out of place, assessment for hypermobility spectrum disorder is worthwhile. Strengthening and control exercises are the main treatment.
A pop at the time of injury
A loud pop during a twist or fall, followed by pain and swelling, can indicate a ligament tear, such as of the ACL, a meniscus tear or a dislocation. This needs prompt assessment.
See meniscus tear.
When popping is painful
- Locking, catching or the joint giving way.
- Swelling, warmth or redness.
- Pain that persists after the noise.
- Reduced range of movement.
These signs suggest a mechanical problem or inflammation rather than harmless gas.
Is it bad to crack your own joints?
Occasional self-cracking of knuckles or the back is generally harmless. Forceful twisting or getting others to crack your neck can strain tissues. If you feel the urge constantly, stiffness may be better addressed with movement and exercise.
See neck cracking.
Keeping joints healthy
- Stay active with regular movement.
- Strengthen the muscles around the joints.
- Warm up before exercise.
- Maintain a healthy weight.
- Vary posture and avoid long periods still.
Assessment
A physiotherapist or doctor asks about the noise, pain, injuries and other joints, then examines movement, stability and strength. Imaging is used only when a structural problem is suspected.
Popping during exercise
Knees, hips and shoulders often click during squats, lunges or overhead lifts. If it is painless and does not limit movement, it is safe to continue. Adjusting technique, warming up and building strength gradually can reduce noisy joints.
When to see a professional
- A pop with injury, followed by swelling.
- Popping with pain, locking or instability.
- Hot, swollen, red joints.
- Joints slipping out of place.
- Popping with numbness or weakness.
Key points to remember
- Most joint popping is harmless.
- Gas bubbles and sliding tendons cause most noises.
- Knuckle cracking does not cause arthritis.
- Popping with pain, swelling or locking needs assessment.
Questions about joint popping
These answers are general information and do not replace an examination or individual medical advice.
Why do my joints pop so much?
Gas bubbles, sliding tendons, hypermobility or stiffness after rest.
Is joint popping bad?
Usually not, unless it comes with pain, swelling or locking.
Does cracking knuckles cause arthritis?
No, studies have not found a link.
Why do my knees crack when I squat?
Usually harmless noise from the kneecap or tendons.
Can popping joints be a sign of arthritis?
Grinding with pain and stiffness can be; noise alone is not.
Why can’t I crack the same joint twice?
It takes about 20 minutes for the gas to dissolve again.
Is popping normal in hypermobile people?
Common, but painful popping should be assessed.
Should I worry about a pop during sport?
Yes, if followed by pain and swelling.
Can exercise reduce joint popping?
Strengthening may reduce some noises and helps joint health.
Is it bad to crack your back?
Occasional self-cracking is generally harmless.
Sources
- NHS · Joint pain
- deWeber K et al. Knuckle cracking and hand osteoarthritis. J Am Board Fam Med. 2011
- Kawchuk GN et al. Real-time visualization of joint cavitation. PLoS One. 2015
This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.