When a chiropractor performs an adjustment, the patient’s lower back undergoes quick and gentle stretching of the spinal joint. The patient might hear a popping noise as the joint is opened as the chiropractor makes adjustments. Research proves that small pockets of air are found in the tissue fluid surrounding the joint capsules. As the chiropractor stretches the patient’s joint tissue during a chiropractic adjustment, the pockets of air “pop” as they shift.