When your knees pop during squats or your wrists crack during push-ups, it’s easy to wonder what’s going on in there? Is it dangerous? Is something out of place?
Joint noises are incredibly common, especially during movement. In most cases, they’re harmless. But some sounds can signal underlying issues worth paying attention to. Here’s what the science says about popping knees, cracking joints, and when it’s time to be concerned.
1. Cavitation: The Science Behind “Cracking” Sounds
The most common reason your joints make noise, especially that sharp crack or pop, is a process called cavitation, specifically a type known as tribonucleation. This occurs when dissolved gases, mostly nitrogen, form a gas cavity in your joint fluid as pressure drops during movement.
It is the same process behind knuckle cracking. When a joint is pulled or stretched, the space within it expands slightly. That pressure drop causes gases to come out of solution and rapidly form a bubble. The sound comes from the formation of that bubble, not its collapse (1).
💡 Key Takeaway: That cracking sound when you move is not bone grinding. It is gas forming in joint fluid as pressure changes, which is totally normal and generally harmless.
2. Ligament and Tendon Movement Over Bone
Another common source of noise, particularly in the knees, hips, and shoulders, is the snapping of a tendon or ligament over a bony prominence. This is sometimes called a “snapping joint.”
For example, the iliotibial (IT) band may snap over the outside of the femur during deep squats, or a hamstring tendon may shift as the knee flexes. These noises are often harmless if they’re not accompanied by pain or swelling. However, repetitive snapping can sometimes lead to irritation or inflammation (2).
💡 Key Takeaway: Snapping or clicking sounds during motion often come from tendons or ligaments moving over bones. These are usually safe unless accompanied by discomfort.
3. Cartilage Wear and Degeneration
In cases where popping is frequent and accompanied by pain, especially in older adults, cartilage changes may be involved. In knees, this might indicate early osteoarthritis or patellofemoral tracking issues.
As cartilage wears down, the surfaces inside your joints become less smooth. This can cause crepitus, a grinding or crackling sensation, and result in noise during movement (3).
💡 Key Takeaway: Persistent popping with pain, swelling, or instability could point to cartilage damage or degeneration. If that’s the case, it’s worth checking in with a healthcare provider.
4. Exercise and “Noisy” Joints
In the fitness world, popping knees during lunges or squats are extremely common. The good news? As long as the sounds aren’t accompanied by pain, loss of motion, or swelling, they’re not a red flag.
In fact, joints may make more noise when they’re tight or when you’re warming up. As your tissues become more hydrated and mobile during a workout, those sounds often diminish.
💡 Key Takeaway: Noise during training isn’t a problem by itself. Prioritize mobility work, slow warm-ups, and progressive loading to help joints move more quietly over time.
5. Joint Health Tips: Supporting Long-Term Mobility
Even if joint noises are normal, taking care of your joints can reduce discomfort, prevent wear, and support long-term function.
Tips to support joint health:
- Warm up thoroughly before intense exercise
- Stay hydrated
- Incorporate mobility drills and dynamic stretching
- Strength train to support the muscles around joints
- Maintain a healthy body fat percentage to reduce joint load
✏︎ Bottom Line
Not all pops are bad. In fact, most joint noises are harmless and just part of your body’s natural mechanics. Cavitation, tendon movement, or tight connective tissue are often behind those clicks and cracks.
But if popping is frequent and comes with pain, stiffness, or swelling, don’t ignore it. That could signal an underlying issue worth addressing.
At PlateauBreaker, we don’t just focus on appearance. We care about how your body feels and functions. Our blog posts are designed to educate and empower you with information that matters. A sustainable fat loss strategy should include movement that supports your joints, muscles, and long-term vitality
Sign up now and start making smarter moves. One smart decision at a time.
Want a clear, effective path to sustainable fat loss?
Sign up for the PlateauBreaker™ Plan and start your fat-loss journey today.
Bibliography
- Kawchuk, Gregory N et al. “Real-time visualization of joint cavitation.” PloS onevol. 10,4 e0119470. 15 Apr. 2015, doi:10.1371/journal.pone.0119470. https://pubmed.ncbi.nlm.nih.gov/25875374/
- Groh, Megan M, and Joseph Herrera. “A comprehensive review of hip labral tears.” Current reviews in musculoskeletal medicine vol. 2,2 (2009): 105-17. doi:10.1007/s12178-009-9052-9. https://pubmed.ncbi.nlm.nih.gov/19468871/
- Hunter, David J, and Ali Guermazi. “Imaging techniques in osteoarthritis.” PM & R : the journal of injury, function, and rehabilitation vol. 4,5 Suppl (2012): S68-74. doi:10.1016/j.pmrj.2012.02.004. https://pubmed.ncbi.nlm.nih.gov/22632705/
