Why do I hear a ‘Click’ during spinal manipulation?
Osteopaths use a technique called High Velocity Thrust (or HVT). This is a safe, relatively gentle spinal manipulation to restore normal movement and function in the joints of the spine. It 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 hear a clicking or popping noise. However, the noise is perfectly normal is not the sound of a bone crack!
So what is actually happening to cause this sound?
The sound is believed to come from the release of gas bubbles from the joint to which the HVT technique is being applied. Joints are the meeting point of two separate bones. They are held together and in place by connective tissues and ligaments and surrounded by synovial fluid. Just like when you stretch or bend your finger to pop the knuckle, the bones of the joint are pulled apart. The connective tissue capsule that surrounds the joint becomes stretched.
This stretching rapidly increases the volume and decreases the pressure in the joint cavity. As a result this causes the gases dissolved in the synovial fluid to become less soluble and form bubbles. When the joint is stretched far enough, the pressure in the capsule drops so low that these bubbles burst. This produces that ‘pop’ that we associate with joint manipulation. See this demonstration.
Does the popping sound always occur?
Patients often listen for the tell-tale noise as a sign that the HVT has worked. However, a pop or click noise will not always be heard – even if a joint has been released. The relaxation of the surrounding muscles and increased movement in the joint are far more important signs of the technique having worked.