Why do my knees make noise?
Snap, Crackle, Pop: Joint noises, are they normal? Why do my knees sound like rice krispies? Most likely there has been a point in time where you have heard a loud pop or crack while performing an activity. Whether your ankles pop walking up or down the stairs, or your knees crack while squatting to pick something up from the ground; joint sounds are fairly common. There are various types of joint noises, also in the medical community referred to as crepitus, that are classically associated with different causal factors. However, are joint sounds and noises a point for concern? Sometimes these noises can take us by surprise and can incite fear about functional ability or structural damage, therefore it is important to take a step back and learn what causes it.
First off, it is important to differentiate between physiological and pathological joint noise. Physiological being quite common and not linked to specific impairment or limitation while pathological is connected to changes such as swelling, pain or a history of injury.1 Commonly, pathological joint noise is characterized by high frequency and gradual aggravation.1 Although, pathological joint noise can be further broken down into acute and chronic subcategories. Acute onset is typically seen with meniscal or ligament injury with a clear mechanism of injury, such as loud pop heard with a twisting and planting of the foot followed by relatively immediate pain and swelling. Chronic pathological noise occurs more gradually, and may be caused by old meniscal tears, cartilage injury, arthritis, or patellofemoral pain syndrome that gradually causes increased pain and/or swelling. These types of joint noise are less common than their physiological counterparts. It is also important to note your own personal feelings that are associated with the joint noise. Our brains are adapted to identify danger, if we perceive a noise to be indicative of injury or structural damage we are also more likely to experience pain - pathological and physiological noise alike. Physiological joint noises are the most common and are not a point of concern however, if you are experiencing pain or swelling with joint noise it may be time to discuss with your physician or consult a physical therapist to allow you to return to the lifestyle you want without an increase in symptoms.
““This is the question we as therapists have been asked more than any other in my career. Why do I have popping and cracking and how do I get it to stop.””
Joint noises can be challenging to categorize as each individual may provide a different description of a specific sound, though there are basic terms that are more common and will be explained below. Prehab guys has also released an article with this information in a streamlined chart formation that can be more easily digestible. The most common sound descriptors are as follows; pop, clicking, clunking, creaking, cracking/popping, snapping, gritty/grating sounds.
An isolated “pop” when associated with a trauma- as forementioned in acute pathological noise- and/or and swelling is commonly associated with tissue injury such as a muscle or ligament strain or sprain.“Snapping” has been attributed to tendons moving over bony prominences on the body. As our bodies move, so do our muscles and tendons! Occasionally this type of sound can be indicative of tight musculature though many times there is no singular cause.2“Clicking” is similar to snapping in that, when unaccompanied by swelling, it is largely associated with the movement of tendons over bony prominences or even over each other. Clicking accompanied with swelling is more likely to be associated with meniscal lesions or other intra-articular pathologies.“Creaking” is likened to the sound of a door that needs some WD-40. Your joints are the same-- without proper lubrication, they may be a little louder than usual. You may find this sound is more common in the morning time or after a period of rest as the tissues and joints are at a lower temperature. Merkher et. al. found that lubrication of a cartilage surface by synovial fluid is impaired at low temperatures.3 Decreased lubrication means increased friction forces.
The best way to warm those joints up? Movement! There’s a reason you may have heard your physical therapist say the phrase motion is lotion.“Clunking” can be described as a loud noise occurring due to a release against resistance.1 It has also been associated with structures that are jostling for optimal positioning with movement.“Popping/Cracking” sounds are one of the most common, this can be caused by changes in joint pressure which can lead to tiny bubbles of gas forming in the joints, when these bubbles are rapidly formed they can make a popping noise. This kind of sound is usually the sound that is made when someone intentionally “cracks” their knuckles or receives treatment from their local chiropractor.1“Grating/gritty” sounds are commonly associated with osteoarthritis, as this can occur when the surfaces of our joints become rougher. Overall, it’s important to note that this noise is not inherently harmful or indicative of dysfunction. This sound actually is an indication that your knees are moving well and lubricated within the joint, although the joint surfaces are rough, movement is still able to occur.
“General movement is a necessity for daily living. The longer you can continue to move typically the higher the quality of life.”
Physiological joint noises are the most common and are not a point of concern. However, just as a reminder, if you are experiencing pain or swelling with joint noise it may be time to discuss with your physician or consult a physical therapist to allow you to return to the lifestyle you want without an increase in symptoms. Most joint noises are not inherently associated with tissue damage and vibration arthrography found 99% of knees make noises.4 Although you may be annoyed by your musical joints, if they are not accompanied by pain or swelling it is usually best to embrace the orchestra that is the human body!
AUTHOR:
Kamy Brandt, PT, DPT
Physical Therapist LWPT Kirkland
CONTRIBUTORS:
Dr. Chris Boone, MD
Proliance Sports Medicine Physician & Orthopedic Surgeon
Dr. John Manning, MD
Evergreen Health Orthopedics & Sports Medicine
Ben Wobker, PT, MSPT, CSCS, CFSC, SFMA
Founder & Director LWPT
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REFERENCES
Song SJ, Park CH, Liang H, Kim SJ. Noise around the Knee. Clin Orthop Surg. 2018;10(1):1-8. doi:10.4055/cios.2018.10.1.1
Robertson CJ. Joint crepitus - are we failing our patients? Physiother Res Int. 2010;15(4):185-188. doi:10.1002/pri.492
Merkher, Y., Sivan, S., Etsion, I. et al. A rational human joint friction test using a human cartilage-on-cartilage arrangement. Tribol Lett 22, 29–36 (2006). https://doi.org/10.1007/s11249-006-9069-9
McCoy G, McCrea J, Beverland D, Kernohan W, Mollan R. Vibration arthrography as a diagnostic aid in diseases of the knee. A preliminary report. The Journal of Bone and Joint Surgery British volume. 1987;69-B(2):288-293. doi:10.1302/0301-620X.69B2.3818762
Disclaimer: The information listed on this page is not to be used as medical advice. If you have any questions or concerns regarding stretching, mobility, or strength training, please seek out professional attention.