My knee cracks and pops! Here are three reasons why you DON’T need surgery

I recently had a patient who had come in for a consultation with minimal knee pain. When he came to me, he was worried, distressed and anxious.

Why? 

Because his doctor had told him that he might need a total knee replacement, as the cracking in his knees “…didn’t sound good”. However, this is an absurd notion, and this blog post is here to help you understand why. Fortunately, knee cracking, popping and snapping sounds in the knee are a common and completely normal process in the knees.

Physiological vs pathological sounds 

The vital differentiation in knee sounds is the presence of ‘painful sounds’ versus ‘non-painful sounds’. In more formal terms, physiological (normal knee sounds) versus pathological knee noises (Song et al., 2018). In most cases, many individuals have normal physiological knee noises, which are associated with: 

  • No worsening of sounds or increased symptoms (such as loss of ROM, increases in pain, decreases in functional ability) 
  • No association with a history of injury 
  • Sporadic or inconsistent noise characteristics (e.g. Usually the most common way to describe this is: “It sometimes cracks, but other times doesn’t.”) 

Pathological noise is often associated with symptoms such as: 

  • Swelling and effusion in and around the joint
  • On injury, a loud “POP” sound with pain was noticed 
  • Consistent cracking with careful examination 

A proper assessment and diagnosis will need to be completed by your physiotherapist to create an accurate diagnosis of your knee pain. In this situation, a trip to the doctor is not always necessary, as physiotherapists can assess and diagnose your knee pain and other surrounding tissues.

What EXACTLY causes noises in the knees? 

Physiological Knee Noise

The exact origin of normal, physiological knee noises is variable. Some proposed mechanisms include: 

  • Buildup or bursting of tiny bubbles in the synovial fluid 
  • Ligaments and tendons may stretch as over a small bony lump and then snap back into place – causing the clicking sound 
  • Catching of the synovium or physiological plica
  • Hypermobile meniscus 
  • Discoid meniscus 
  • After surgery 

(Song et al., 2018)

The buildup of cavitation bubbles in the synovial fluid of the knee joint is the commonly circulated explanation for knee joint noises. The sudden collapse of the bubble during regular joint movements can create the “popping” sound. The nature of this sound is sporadic due to the air buildup, which means that immediately after cracking your knee, it’s often hard to reproduce the same sounds again. 

Pathological Knee Noise 

There are many causes of pathological noise, which include degenerative changes (i.e. osteoarthritis), pathological plica, patellofemoral instability, pathological snapping knee syndrome and post-surgical crepitus (Song et al., 2018). 

The Osteoarthritic Knee 

The general characteristics of osteoarthritis may cause crepitus in the knee secondary to osteoarthritis—namely, gradual loss of cartilage, development of bony spurs and cysts. Crepitus in the knee can be synonymous with symptoms of patellofemoral osteoarthritis. 

It comes at no surprise that greater severity of knee osteoarthritis is highly correlated with more significant pain levels and decreased functional abilities (Neogi et al., 2009; Sowers et al., 2011). Those with the highest pain had a higher likelihood and severity of pathological abnormalities such as: 

  • Full thickness cartilage defects 
  • Synovitis 
  • Complex or mascerated meniscus tears 
  • Large osteophytes 

(Neogi et al., 2009; Sowers et al., 2011)

However, exercise can slow the progression and development of knee osteoarthritis (Bosomworth, 2009). In some cases, there is an associated improvement in pain and function in those who perform regular moderate exercise compared to those who engage in sedentary lifestyles (Bosomworth, 2009). 

So what is the management of knee noises and/or osteoarthritis? 

Managing ‘noisy knees’ really does depend on the underlying reason and the presence of physiological knee noise vs pathological knee noise. Like many other joints or spine-related pathology/pain, the most significant factor for knee noise may be the psychological factors associated with the sound or feeling. For those who don’t understand the fundamental reasoning behind knee noise, they may have anxious and negative thoughts, which can lead to decreased self-confidence, avoidance of movement/exercise and just general heightened sensitivity to any stimulus around the knee. Unfortunately, many times this may be compounded by your surrounding family and friends (unintentionally) when they make comments such as: 

  • Those knees make you sound 20 years older 
  • You have old people’s knees
  • Your knees sound arthritic
  • That doesn’t sound good for your knees 

It is important to remember that knee noise isn’t something we need to worry about unless there are painful or functional changes to your knee. However, you should attend an appointment with your local physiotherapist if you have ongoing concerns.

Have a look at my knee taping guide and knee pain guide to get you started if you have concerns about your knee pain!

Final thoughts

Knee noises are scary if you don’t know what causes them. Most noise in your knee is generally non-painful physiological noises, which are naturally occurring sounds that happen in almost every person’s knees. If you have ongoing pain or functional limitations associated with the noise, then the recommendation would be to seek out your local health practitioner to get it checked. 

In the meantime, it’s important to keep moving and keep exercising as you can! As this has the best chance of delaying chronic conditions like osteoarthritis of the knees. 

Do you have noises in your knee? 

References

  • Bosomworth N. J. (2009). Exercise and knee osteoarthritis: benefit or hazard?. Canadian family physician Medecin de famille canadien, 55(9), 871–878.
  • Neogi, T., Felson, D., Niu, J., Nevitt, M., Lewis, C. E., Aliabadi, P., Sack, B., Torner, J., Bradley, L., & Zhang, Y. (2009). Association between radiographic features of knee osteoarthritis and pain: results from two cohort studies. BMJ (Clinical research ed.), 339, b2844. https://doi.org/10.1136/bmj.b2844
  • Song, S. J., Park, C. H., Liang, H., & Kim, S. J. (2018). Noise around the knee. Clinics in Orthopedic Surgery, 10, 1 – 8. 
  • Sowers, M., Karvonen-Gutierrez, C. A., Jacobson, J. A., Jiang, Y., & Yosef, M. (2011). Associations of anatomical measures from MRI with radiographically defined knee osteoarthritis score, pain, and physical functioning. The Journal of bone and joint surgery. American volume, 93(3), 241–251. https://doi.org/10.2106/JBJS.I.00667