Firstly, joint manipulation or adjustment is moving the joint just beyond the elastic range, which is different from just ‘mobilising’ or stretching, where usually no joint sounds occur.
There are basically two types of joint sound that need to be distinguished:
- The clearer, louder joint ‘pop’ with a Chiropractic adjustment, manipulation or cavitation, which are three interchangeable terms.
- The repetitive joint rubbing or grating, creaking, graunching or ‘crepitus’ sounds
Joint ‘pops’ with Chiropractic adjustment
Joints are lubricated by synovial fluid which contains oxygen, nitrogen and carbon dioxide, helping to ‘oil’ the joints and keep them moving smoothly. It also provides nutrients to help maintain healthy joint surfaces. It is a volatile and is held as a fluid under normal joint pressure. The ‘crack’ or ‘pop’ sound occurs during a joint manipulation. It can happen naturally, or we can get into habits of doing it ourselves, for example if we click our own fingers.
This is of course a simple explanation, and in many ways, we still don’t know exactly what causes the sounds. Below are two theories as to how the popping sounds are created:
1. Bubble Formation theory
As the joints are stretched, a vacuum is created, and this changes the synovial gases from fluid into tiny gas bubbles. As the vacuum increases within the joint fluids, the bubbles come together until they form one sizeable bubble, which then bursts with a “pop”. This is painless and happens in a split second. A similar analogy is if you use a vacuum bottle pump to save wine from oxidation you can see how bubbles form in the wine if too much air is extracted and there is a ‘pop’ when you remove the stopper. Cavitation is also defined as the formation of partial vacuums in a liquid by a swiftly moving solid body.
2. Suction Cup Release theory
A synovial fold in a joint is believed to behave very similarly to a suction cup as joint surfaces are held together and the negative pressure already exists. If an elastic cup is pushed down onto a polished surface, it removes all air. As the cup is distracted or pulled away it stretches, the air is subjected to increase in volume, and a pressure differential holds the edges of the cup onto the surface until it reaches its elastic barrier. A ‘crack’ sound is heard as the edge of the cup lifts, and air quickly rushes in to the space to equilibrate the vacuum creating a sound wave through waves of condensation and rarefaction
Please read https://dynamicdiscdesigns.com/synovial-fold-noise-suction/ for more information.
Joint settling after a Chiropractic Adjustment
The ‘pop’ sound of a joint adjustment is usually clearly defined. After an adjustment it takes about 20 minutes for the joint gases to reabsorb (‘refractory period’), whilst the pressure in the joint returns to normal. During this time you will not be able to elicit another joint pop. After this it may be possible to pop the joints again, although it is not advisable straight away.
Joint Ranges of Movement
During a joint adjustment the joint is taken beyond the elastic limit (1) into the orange ‘paraphysiological range’ which reduces the pressure temporarily, and causes the sounds as gas bubbles release. This can greatly increase the mobility in the joint, in a way that joint mobilisation or stretching can’t achieve.
Anatomical Joint Range of Movement
Ranges of Movement in diarthrodial joints:
- Active Movement: The amount you can move yourself, by muscular action.
- Mobilisation or Passive Stretch: The amount of movement when a joint is stretched, or for example in physiotherapy, yoga or by your Chiropractor up to the elastic barrier.
- Adjustment/Manipulation: Motion achieved during a Chiropractic adjustment or manipulation, with or without an audible release beyond the Elastic Limit (1) into the paraphysiological space
- Strain or Injury: beyond the normal Anatomical limit (2), which can damage ligaments and tear the surrounding joint capsule, muscles or ligaments, giving acute pain or inflammation, as well as muscle spasm around the injury.
Other joint sounds
Firstly, be aware that joint sounds don’t always happen. Some people’s joints click more loudly than others and some just don’t seem to give any audible ‘pop’. This can also happen if the joints are very tight or if there is acute muscle spasm around the joint. Please don’t feel cheated if your joints don’t crack as you’ve seen on YouTube videos. With some people the joints just don’t sound, but they have still been released and stretched effectively to restore their movement.
Muscle, ligament or tendon sounds that are not full joint ‘pops’
Crepitus, grinding, graunching, grating, creaking, crunching are all words to describe the repeated sounds that happen during the rubbing of tendons, ligaments, muscles or scar tissue. For example, this could manifest itself as ‘noisy’ shoulders every time the arms are stretched, or when getting up from squatting or sitting, especially after periods of inactivity.
Inflammation or joint injury
If there is swelling or excess fluid in a joint, movement can cause sounds. A rotator cuff shoulder injury, for example, tends to creak every time the arm is raised or moved though a specific range or movement.
Repetitive clicks or snapping
Caused by misaligned connective tissue or even nerves. For example, the ulnar nerve can slip in and out of its ulnar groove each time you flex and extend your elbow.
Joint rubbing through loss of cartilage
As arthritic joints lose their smooth cartilage there can be scar tissue in the joint, or the bones rub together on a rougher, more unstable surface.
Ligaments are fibrous tissues that connect two bones at a joint. Tight ligaments are prone to popping when they are suddenly moved, which sometimes results in short-lived pain in the area.
Tendons are fibrous tissues that connect muscle to bone and can also cause popping noises around a joint. This is most commonly found in snapping hip syndrome which causes a snapping sensation when the hip is flexed and extended.
After joint injury or surgery, scar tissue, known as adhesions, is formed by the ligaments which are more prone to popping and cracking. Common examples are shoulder rotator cuff injuries and fibrous adhesions in the lungs, which can give a rasping breathing sound.
Two types of joint sounds that may require treatment
Ripping or tearing sounds
Ripping or tearing noises, especially if heard during a fall or accident, could be a sign of a torn muscle, ligament or tendon, particularly if this is accompanied by pain, swelling or bruising.
This can be a louder pop with a feeling of movement of a muscle or ligament over a bone. It can be disconcerting and repetitive. This type of sound is commonly heard in the shoulder, as the tendons ‘snap’ when the arm is raised, or on hip flexion or outward rotation as the muscles roll over the hip.
If you have any concerns or questions about joint sounds, please contact us at the Back Care Clinic.