Updated: Nov 23, 2020
By Dr. Ashley O'Rourke PT, DPT, ATC, LAT
This is by far one of the most commonly asked questions I get as a physical therapist. The short answer is: the majority of the time, no, however there are some exceptions. Read below to find out what they are.
This is probably the most frequently asked question I get on a day to day basis. A patient will be on the table and say to me "my shoulder cracks every time I raise my arm...is that bad?" or "I feel a click in my knee every time I extend it...how do I get it to stop?" The reality is that there are many explanations for these sounds- most of which are often completely harmless if not accompanied by pain. There are, however, some cases in which the sounds should be addressed with the general rule of thumb being: any of these sounds occurring in a joint that are not accompanied by pain are typically nothing to worry about. Let's differentiate:
All joints are surrounded by synovial fluid. Think of this as your body's natural oil. It lubricates the joints to decrease friction between the surfaces. Changes is pressure- which can occur with movement- can cause gas bubbles to form within the fluid. When these bubbles implode or "pop" the sound associated with "cracking your knuckles" is produced. To physical therapists and chiropractors this sound is known as a "cavitation". They are painless, do not cause damage and often times even relieve symptoms (at least temporarily). It takes time for this gas to build back up which is why you cannot repeatedly crack the same joint over and over and over again. While one should not be worried about cracking their knuckles from time to time, repeated attempts over a short period of time should be avoided as this can eventually cause changes in the joint capsule or train the brain into thinking they "need" to perform this activity over and over again (forming a habit) when in fact it is not necessary.
That being said, a "popping" sound coming from the lower leg that occurs after landing from a jump shot while playing basketball or in the knee after cutting/pivoting on the soccer field could indicate serious injury such as an achilles rupture or ACL tear- both of which would most often be heard/felt in conjunction with pain.
There are other sounds that are not serious, but overtime could lead to chronic injury. An example of this could be snapping in the outside of the knee. In the beginning this snapping sensation may be quite annoying, but not cause any pain. It is by no means an emergency, however, with repetitive motion and frequent activity this friction that occurs as the connective tissue (iliotibial band) rubs against and snaps over the thigh bone can cause inflammation and irritation of the tissue leading eventually to pain. Similarly, people can experience a like feeling in the hip known as "snapping hip phenomenon". This can be due to tightness in the muscles/tendons rubbing over the bone.
This sound can sometimes be problematic if it is a result of connective tissue abnormality such as a torn meniscus in the knee or torn labrum in the shoulder/hip. These would both be typically associated with pain. Additionally, sometimes a clicking sensation can be felt in the knee cap which can be indicative of a tracking issue where the knee cap does not stay perfectly in the groove that it is meant to stay in. While this may not cause additional symptoms in the short term, it too could cause pain in the long term like patellofemoral pain syndrome (PFPS) or generalized knee pain caused by muscular imbalances that lead to abnormal stresses to be placed upon the knee.
This sound/sensation can be a little more concerning and indicative of instability or laxity in the joint leading to subluxation or full dislocation. People with joints that are "too loose" may experience clunking when the two joint surfaces rub together. Seeking treatment would be indicated to work on stability of the joint through strengthening the tissue around it in order to prevent dislocations that could result in tissue damage such as torn ligaments/joint capsule damage etc.
This type of sound is most often associated with general degeneration of cartilage within a joint, such as osteoarthritis and occurs when there is bone on bone contact. This sound may increase over time as it is normal for joint surfaces to change with age.
Sometimes a painful or non-painful "pop" can be heard during manual therapy- perhaps while a PT is moving a knee after surgery. This sound can be indicative of the breaking up of scar tissue and may be beneficial if it leads to improved mobility.
**If you are uncertain whether you are experiencing a normal joint sound or something problematic let the qualified doctors at Tidal Sports Rehab & Recovery assess the tissue to determine whether intervention is warranted.