Snap, Crackle, and Pop
Not a day goes by in our office that we don’t discuss the noises that body joints make. Hip joints snap, backs cracks, knuckles pop, knees grind… What the heck are all of these noises? Should you worry about them? Are they abnormal? Let’s unpack it all.
Let’s start with what we DO find concerning: a painful ‘POP’ followed by swelling. Noises followed by swelling is generally not a good thing. It’s characteristic for a strain, sprain or tear of a ligament, muscle or tendon. No bueno. This would be an isolated event, meaning you are unable to replicate the ‘pop’ sound.
Now that we have that out of the way, let’s discuss the rest of the body joints orchestra.
CRACKING
Good ol’ spine cracks. For many, there is something very satisfying when you feel your spine crack. For others, it’s a sound for concern. There are a lot of myths around joint manipulation and “popping” the spine, so let’s dig in.
MYTH: Spine manipulation aka cracking your back ‘realigns the spine’ or puts the joint ‘back into place’.
The truth, in a nutshell: The sound that you hear when your joints crack (like when you crack your knuckles and your spine is manipulated) is a gas bubble forming:
Research from 2015 demonstrates that the separation or pulling force from cracking a joint (like a knuckle, for example) creates a negative pressure in the joint fluid allowing dissolved gas to escape – this forms a bubble. It takes about 20 minutes for the pressure to build again to be able to crack the joint another time.
The spine crack is NOT your joints moving in/out of position (it’s the gas bubble!) and therefore the spine bones (vertebrae) are not moving back into alignment. The bigger question is, were the spine segments out of alignment to begin with?
The spine is one of the most resilient structures in the human body. Studies have shown that it would require an impact created by a 500lb car crashing into a wall at 30mph to fracture the cervical vertebrae. Injuries to the spine tend to occur when the body does not have an opportunity to tense the supporting muscles. The questions remain: can the vertebrae “pop out” without a high velocity force? If so, can practitioners actually “pop” them back into place?
In order for the theory that maligned vertebral segments are causing pain and therefore need to be realigned, practitioners would need to agree on which segment is out of alignment and perform a targeted treatment. There was a study performed comparing two expert palpators in identifying the stuck or dysfunctional vertebrae in 12 patients – the findings demonstrated poor reliability between the two practitioners. Additionally, in 2004, a study looked to see if the sound of cavitation (the spine crack) was specific to the treatment area it was intended for. There was no significant correlation between the treatment technique selected and the anatomical location of the cavitation sounds. Finally, a systematic review in 2016 concluded the evidence of spinal manipulation has no effect on segmental vertebral motion.
So, why do back cracks (spinal manipulations / adjustments) feel so good if they aren’t realigning your spine segments? This is because manipulations create a neurological effect which leads to short term pain relief. In fact, a study in 2013 demonstrated that subjects had immediate pain relief in the lower back whether the manipulation occurred in the lumbar region OR thoracic region. This is GREAT NEWS because even if someone’s lower back pain is really flared up we can provide temporary relief performing a manipulation not even in the same area!
Key Takeaways: If you crack your knuckles or a practitioner cracks your back, that sound is a tiny gas bubble forming. The manipulation isn’t your spine “going back into place,” and the crack can provide a brief period of pain relief.
MYTH: Cracking your knuckles will give you arthritis.
This might be our favorite and you’ve definitely heard this myth before. It likely stemmed from an annoyed parent trying to get their kiddo to stop popping their knuckles. There is a ton of research on this topic and we will just cut to the conclusion: cracking your knuckles does NOT give you arthritis.
SNAPPING & POPPING/CLICKING
We see this a lot in the hips, shoulders, and ankles. At a specific spot in the movement you’ll hear a ‘snap’ or ‘click’ and it’s reproducible with every or nearly every repetition. This is similar when reaching the arm overhead or performing ankle circles.
Since these noises are readily reproducible, they are NOT gas bubbles in the joint as described earlier because there is time needed in order for the pressure gradient in joint fluid to change in order to form a bubble. If it’s not tiny bubbles, then what is it? And, should you be concerned?
These snaps and clicks are the sounds of moving tissues. Should you be worried? If it doesn’t hurt, and most of the time these noises are asymptomatic, there is no need to worry.
Our shoulder is a ball and socket joint and has been compared to a golf ball (humeral head – arm bone) sitting on a tee (shoulder blade - joint surface) aka it is relatively unstable and relies on muscles for stabilizing support. The clicking and popping that you hear is simply the supporting structures (muscles, tendons, bursa) moving on one another.
For the ankle and hip, this is likely tendons slipping over bone. As long as this isn’t painful, it really isn’t anything to be concerned of.
Snapping in the front of the hip is caused by either the rectus femoris (one of the quadriceps muscles) moving across the femur (long leg bone) or the iliopsoas (hip flexor) moving over bony prominences on the pelvis. The remedy for this? Improving tissue mobility and strengthening. Oftentimes the snapping is occurring on the weaker side, which tends to be the tighter side.
The Takeaway: this is common and the snapping/popping isn't a reason to panic – you aren’t damaging your body, but it is a good idea to start to mobilize and strengthen the supporting structures of that joint to create better right / left symmetry.
“MOTION IS LOTION”
Crepitus: grinding/creaking joint sounds.
Crepitus is common in knee joints and the cause is due to cartilage rubbing on joint surfaces or other soft tissues surrounding the joint. The patella (knee cap) is supposed to glide smoothly over your femur (leg bone) during bending and straightening of your knee. Over time, the joint surfaces become rough and can lead to the creaking sensations that you hear. Generally, this isn’t a big deal, however as we continue to age and the cartilage continues to wear, it can lead to arthritis. THAT SAID, a longitudinal study published in 2019 concluded that the presence of knee crepitus DID NOT lead to higher odds of having a knee replacement due to osteoarthritis.
The bigger picture: Staying active and a healthy body weight helps take load off of your joints and strong muscles provide support. Motion is lotion for our joints. Cartilage does not have great blood supply and relies on movement to bring blood and nutrients in/out to keep it healthy and strong. So, if your knees crunch as you squat up and down, don’t stop. Rest is almost never best - stay moving to keep your joints strong.
Conclusion: a pop followed by pain/swelling is not good and reason to seek medical advice. As for the rest of the sounds that our body makes, rest assured that they aren’t reason to be immediately concerned.
Stay Moving,
THE BPT TEAM