Practically every lifter has heard their own knees emit a popping noise as they bend them, occasionally leading to concern over whether this noise is a sign of anything negative or not.

Fortunately, your knees cracking - whether during the squat or any other movement - is for the most part, entirely normal and indicates nothing negative whatsoever.

Cracking of the knees when squatting is caused by tiny gas bubbles within the friction-reducing fluid of the joint, often due to these bubbles popping or being rapidly shunted in one direction and thereby producing a sharp noise that can even be heard outside of the knee itself.

Is it Dangerous for the Knees to Crack While Squatting?

In nearly all cases - no, the knees producing a popping or cracking sound is not indicative of any sort of condition or injury whatsoever. It can occur in individuals of all ages and backgrounds, and is primarily due to the aforementioned gas bubbles within the synovial fluid of the joints.

This, of course, assumes that there is not already a physiological injury of the knees already present within the individual, and that they are not predisposed to certain conditions of the knee joint or the connective tissues that form it.

A More Technical Look into Knee Cracking

Regardless of the actual underlying cause of this knee cracking noise, the medical community has grouped practically all noises made by joints under the term “crepitus”, which encompasses sounds such as grinding, popping or the aforementioned cracking sound made by any joint in the body.

In most cases, it is known as benign crepitus - meaning that no adverse health effects are being experienced, and that the crepitus is not a cause for clinical concern. 

However, if the crepitus is accompanied by symptoms of pain, tingling or a reduced range of knee motion, it is possible that the lifter has sustained an injury that requires medical attention and physical rehabilitation.

How to Reduce Cracking of the Knees When Squatting

While benign crepitus is unlikely to cause any discomfort or actually be a sign of anything harmful, it can indeed be unpleasant for some individuals. 

As such, it would make sense that they may wish to reduce the incidence of this popping noise, especially when working out at the gym.

1. Mobility Drills

Performing dynamic stretches and a host of other mobility-focused movements can improve the flexibility of the knee joint, reducing the chance of gas bubbles popping in an abrupt manner. 

Furthermore, performing a lower body mobility drill immediately before performing a set of squats can prematurely pop the gas within the synovial fluid of the knees, reducing the force with which the bubbles will rupture as they are placed under load.

In particular, stretches and movements like the knee-up, the quadriceps extension stretch and the single-leg squat hold are among the most effective at targeting the knee joint and surrounding musculature that directly influence the knee.

2. Perform Quadriceps and Hamstring Isolation Movements

In certain cases, the knees cracking while performing a squat is simply due to excessive pressure being placed on the joint itself, often due to weakness in the two main muscle groups responsible for the knee extending or flexing during a squat repetition.

To reduce the incidence of benign crepitus of the knee, performing targeted isolation exercises that work the quadriceps femoris and hamstrings muscle group is required - the majority of which will also aid in improving the general stability and tissue density of the knee joint itself.

A few examples of effective quadriceps or hamstring isolation exercises are the leg extension, the hamstring curl, the half-rep leg press or the good morning - though the latter is not an isolation movement.

3. Squat with Correct Form

Squatting with poor form can result in excessive pressure being placed on the joints of the knees, leading to a greater likelihood of the gas bubbles within popping and thereby producing the cracking sound that the lifter is trying to avoid.

The greatest errors in squat form that can cause this effect are; leaning too far forward, failing to hold the shins in-line with the ankles, performing the squat with the feet pointed inwards or forwards, and allowing the knees to roll inwards or otherwise allowing knee valgus to occur.

While quite a few more errors can be made in squat form, the aforementioned ones are those that are most likely to cause the knees to crack, as they will shift much of the resistance of the exercise therein. Not only this, but making the aforementioned form errors can often lead to more serious effects, such as knee-related injuries or a general lack of benefit from the squat exercise.

4. Wear Knee Sleeves

One way of reducing pressure placed on the knee joint is through the usage of knee sleeves - a type of fitness equipment specifically made for usage in heavy resistance exercises like the barbell squat or deadlift.

Knee sleeves both compress and provide support to the knee joint, causing a more stable and physically sound knee to be maintained as the exerciser goes through the motions of a squat repetition. This will, in turn, 

Unfortunately, unless performing heavy squat repetitions at a high level, it is best to avoid frequent usage of knee sleeves, as they can lead to weakened stabilizer muscle groups and generally poor squat form due to the lifter failing to develop the correct form habits.

Differentiating Benign Knee Cracking from Dangerous Knee Cracking

The primary way of differentiating between benign or otherwise safe knee cracking and knee cracking that may be a sign of an underlying issue is the presence of simultaneous symptoms, whether at the same time or following the “cracking” noise.

These symptoms can vary in severity and nature, with the most frequently encountered sign that something may be wrong is the accompaniment of pain and instability following the aforementioned cracking sound.

Other signs that your knee cracking may be something more dangerous are that of the knee “sticking” or otherwise possessing a reduced range of motion, tingling or numbness in the knee or surrounding tissues, as well as any sensation of sticking or grinding within the knee itself.

When to See a Physician for Knees Cracking

If you are experiencing any of the aforementioned concurrent symptoms or your knees cracking is becoming an obstacle to your workout plan, it may be time to seek out the advice of a medical professional.

While most cases of knee crepitus are entirely harmless and will not be accompanied by other symptoms, several types of soft tissue injuries or physiological conditions can be associated with knee cracking. 

Torn or otherwise damaged tendons connecting to the patella, arthritis or other degenerative conditions and even a subluxated knee joint are all possible causes of non-benign knee crepitus.

Frequently Asked Questions (FAQ)

Is it Normal for Knees to Crack a Lot?

Yes - it is entirely normal for the knees and other joints to produce a cracking noise, especially when performing rigorous exercise or similar activities. 

So long as this cracking sound is not accompanied by pain, tingling or a loss of joint stability, it is completely safe and a widely occurring phenomenon that happens to people of all ages and lifestyles.

Why do My Knees Sound Like "Rice Krispies" When I Squat?

Unlike the sound of cracking, a grinding or crackling noise as you perform a squat repetition can be a sign of the beginning stages of a degenerative disease - usually in the form of arthritis, though other conditions may also be the culprit.

Medically, all sounds produced by a joint are known as crepitus, with the “rice krispies” sound potentially being a type of non-benign knee crepitus that may require medical attention if accompanied with other symptoms like pain, tingling or a loss of range of motion.

How Can I Strengthen My Crunchy Knees?

While all forms of exercise have a positive effect on connective tissue function, performing repetitive low-impact exercise involving the knee joints can greatly aid in strengthening the tissues therein - especially for individuals who wish to reduce the incidence of cracking or “crunching” sounds being made.

Forms of aerobic exercise like the elliptical machine, cycling or incline treadmill walking can be quite effective at strengthening the knees, as are resistance movements like the squat, lunge or split squat.

Final Thoughts

All in all, your knees making a cracking noise while you squat is not that big of a deal, and definitely shouldn’t be high on your priority list if other issues are also present during your training.

In the event that you do believe that your knees cracking could be indicative of a larger problem, it is best to cease performing the squat and immediately seek out the advice of a medical professional so as to ensure that no serious injuries occur.

References

1. Pazzinatto MF, de Oliveira Silva D, Faria NC, Simic M, Ferreira PH, Azevedo FM, Pappas E. What are the clinical implications of knee crepitus to individuals with knee osteoarthritis? An observational study with data from the Osteoarthritis Initiative. Braz J Phys Ther. 2019 Nov-Dec;23(6):491-496. doi: 10.1016/j.bjpt.2018.11.001. Epub 2018 Nov 16. PMID: 30471964; PMCID: PMC6849337.

2. Song SJ, Park CH, Liang H, Kim SJ. Noise around the Knee. Clin Orthop Surg. 2018 Mar;10(1):1-8. doi: 10.4055/cios.2018.10.1.1. Epub 2018 Feb 27. PMID: 29564040; PMCID: PMC5851845.