The phrase “cracking bones” refers to the manual manipulation of joints, a practice performed by several types of licensed healthcare providers to restore mobility and alleviate discomfort. This action often produces an audible “pop” or “crack,” which is a distinct physiological event within the joint capsule. Understanding the professionals who perform this therapeutic technique is important for anyone seeking musculoskeletal care. The most recognized professional associated with this type of manual therapy is the Doctor of Chiropractic.
The Primary Title: Chiropractor
The professional most frequently associated with joint manipulation is the Doctor of Chiropractic (DC), who specializes in the diagnosis and treatment of conditions related to the musculoskeletal system. Chiropractors primarily use a hands-on technique known as spinal manipulative therapy, often referred to as a chiropractic adjustment. This high-velocity, low-amplitude (HVLA) thrust is a controlled procedure intended to restore proper function to a restricted joint.
To practice, chiropractors must complete extensive education, typically a four-year Doctor of Chiropractic degree program after at least three years of undergraduate study. Their curriculum includes rigorous training in basic sciences like anatomy and physiology, clinical sciences, and a minimum of 1,000 hours of supervised clinical experience. This comprehensive training allows them to diagnose and treat a wide range of human ailments without the use of drugs or surgery, focusing instead on the body’s structural integrity. The goal of the adjustment is not simply to create a sound, but to improve joint function, reduce pain, and initiate reflex actions that can decrease muscle tension.
Other Professionals Who Perform Manipulation
While chiropractors are primary providers of joint manipulation, other licensed healthcare professionals are also trained and qualified to perform similar techniques. Doctors of Osteopathic Medicine (DOs) incorporate manual techniques as part of their comprehensive patient care under the umbrella of Osteopathic Manipulative Treatment (OMT). DOs are fully licensed physicians who can prescribe medication and perform surgery, but they also receive specific training in manipulating the body’s interconnected system of nerves, muscles, and bones.
The OMT approach is holistic, using hands-on methods to diagnose and treat structural and functional issues, though not all OMT techniques involve the high-velocity thrust that produces the audible pop. Physical Therapists (DPTs) also utilize joint manipulation, especially the HVLA thrust technique, as a tool within their scope of practice. Their primary focus is on rehabilitation and restoring movement, and they use manipulation to increase joint mobility and range of motion. The ability of these professionals to perform joint manipulation is determined by their state or national licensing boards and is integrated into a broader scope of practice.
What Causes the Cracking Sound?
The sound heard during joint manipulation does not come from bones cracking, but is a result of a phenomenon called cavitation within the joint fluid. Synovial fluid, the liquid that lubricates joints, contains dissolved gases such as carbon dioxide and nitrogen.
When a joint is quickly stretched or separated during a high-velocity thrust, the sudden distraction causes a rapid decrease in pressure within the joint capsule. This drop in pressure forces the dissolved gases to come out of solution, forming a temporary gas cavity or bubble. The sharp, audible sound occurs when this bubble forms or, more likely, when it rapidly collapses.
Once a joint has cavitated, a “refractory period” of around 20 to 30 minutes must pass before the gases dissolve back into the synovial fluid, allowing the joint to be cracked again. This scientific explanation confirms that the noise is a mechanical event in the fluid, not a fracturing of bone tissue.
Historical and Informal Terms
Historically, individuals who performed joint manipulation without formal medical training were often known by the informal term “bone setter.” This term dates back centuries and refers to lay practitioners who specialized in treating musculoskeletal injuries, including dislocations and fractures, often with varying degrees of skill and safety. The term “bone cracker” itself is a common, non-professional phrase used by the public to describe the sound-producing aspect of the treatment.
While these historical and informal terms persist, they do not denote a modern, regulated healthcare profession. Modern professionals like chiropractors, osteopathic physicians, and physical therapists have replaced the bone setter by integrating these manual techniques into a licensed, evidence-based practice. For safety and effective treatment, it is important to seek care from a licensed professional, such as a Doctor of Chiropractic, who has the required education and diagnostic training.