Why can you hear a popping noise when practitioners manipulate joints?

The work of an osteopath, chiropractor or physiotherapist in treating back and joint pain can involve a specific technique known as ‘High-Velocity, Low-Amplitude Thrust’ or, more simply, ‘High-Velocity Thrust’ (HVT for short).

This is a safe, relatively gentle and pain-free manipulation of a joint in order to restore normal movement and function, whether in the spine or the upper or lower limbs of the body. By applying a short-ranged and fast impulse through the joint, the chiropractor, osteopath or physiotherapist takes the joint just slightly further than it is used to going.  Although it can sometimes feel as if force is being used, the joint is not taken further than it is capable of moving. Sometimes you can hear a clicking or popping noise when the joint is being moved and patients can find this disconcerting at first. However, the noise is perfectly normal and, contrary to the popular misconception, is not the sound of a bone crack. As well as increased mobility, patients can feel invigorated and often report an increased sense of well-being following the procedure.

So what is actually happening to cause this sound?

The sound is believed to come from the release of gas bubbles, mainly carbon dioxide, from the joint to which the High-Velocity, Low-Amplitude Thrust technique is being applied.

Joints are the meeting points of two separate bones, which are held together and in place by connective tissues and ligaments, and surrounded by a clear synovial fluid. When joints are manipulated (like when you stretch or bend your finger to pop the knuckle), the bones of the joint are pulled apart and the connective tissue capsule that surrounds the joint becomes stretched. This stretching rapidly increases the volume and, therefore, decreases the pressure in the joint cavity, causing the gasses dissolved in the synovial fluid to become less soluble and form bubbles. This natural process is called cavitation. When the joint is stretched far enough, the pressure in the capsule drops so low that these bubbles burst, producing that pop that we associate with joint manipulation.

Does the popping sound always occur?

Patients often listen for the tell-tale noise as a sign that the High-Velocity, Low-Amplitude Thrust procedure has worked. However, a pop, click or cracking noise will not always be heard – even if a joint has been released. The larger the joint, the less likely it is to make a popping sound. The relaxation of the surrounding muscles and increased flexibility and movement in the joint are far more important signs of the technique working.

The High-Velocity Thrust technique should only be performed by fully qualified practitioners. A Freedom Clinics Osteopath, Chiropractor or Physiotherapist has trained for 4 or 5 years in the specialised diagnosis and treatment of back and joint pain. This spine and joint manipulation technique will only be used if it is safe and appropriate for the individual patient, and often as part of a variety of other practices including ice, heat, ultrasound, exercise or acupuncture.