K. Jeffrey Miller, DC, MBA
Editor's Note: This article is the first in a series of "dynamic diagnosis" shorts by Dr. Miller as part of his "Continuing your Education" column.
Most patients are familiar with popping and cracking noises that occur during adjustments, and similar noises that emanate on their own from the regions of their musculoskeletal complaints.
The noise patients know as the pop or crack from an adjustment results from cavitation of synovial joints, of course. In the spine, this is usually the facet joints. The noise is produced when a bubble of nitrogen gas within synovial fluid bursts from the shifting of the joint: cavitation.
Patients either love or hate this noise. Many equate it with successful manipulation. Others do not care to hear it, but tolerate it as long as their condition improves. In either situation, it is a good idea to explain the mechanism of cavitation to members of both groups.
The information can be reassuring to patients, and perhaps they will pass the explanation along to others when the subject of the chiropractic "pop" or "crack" comes up. It might make the "pop and crack" discussion less chilling.
Repetitive Crepitus: A Sign of Pathology or Dysfunction
The unique thing about crepitus in a synovial joint is that when it occurs, time must pass before it can occur again. The bubble has to reform. This occurrence is non-repetitive or occasional crepitus.
Non-repetitive crepitus is a natural event. This is opposed to crepitus that repeatedly occurs in and around a joint. Repetitive crepitus is often a sign of dysfunction or pathology.
Repetitive crepitus occurs when cartilage is deranged or degenerated. Repetitive crepitus is audible or palpable with the displacement of the disc in the TMJ joint. Repetitive crepitus from a torn meniscus in the knee is audible or palpable (McMurray's test). Grinding sensations occur from cartilage damage behind the patella with chondromalacia patella (Clark's test).
Repetitive crepitus is also possible with tendon, ligament and retinacular dysfunction. A repetitive popping sound or sensation occurs over the greater trochanter at the proximal femur or over the lateral epicondyle at the distal femur from a tight iliotibial band (Ober's and Noble's tests).
Repetitive crepitus can be experienced at the bicipital groove of the proximal radius when the transverse ligament is torn, allowing the tendon of the long head of the biceps muscle to subluxate (Yergason's test). Ankle injuries can result in a torn retinaculum, allowing tendons to "snap" across the joint.
Whether crepitus is a singular occurrence or repetitive, it is an important clinical event. Its presence can provide an educational opportunity that helps enhance the doctor-patient relationship. It can be an indication of successful manipulation. It is associated with multiple orthopaedic tests, making it a clinical sign helpful in the identification of specific pathologies. It is a wise idea to search for and identify the source of crepitus whenever a patient mentions its existence.
