J Manipulative Physiol Ther. 1995 Feb; 18(2): 65-71.

Analysis of zygapophyseal joint cracking during chiropractic manipulation.

Reggars JW, Pollard HP.

Macquarie University, Centre for Chiropractic, Summer Hill, New South Wales.

OBJECTIVES: To determine if there is a relationship between the side of head rotation and the side of joint crack during "diversified" rotatory manipulation of the cervical spine. DESIGN: Randomized experimental study. SETTING: Macquarie University, Centre for Chiropractic, Summer Hill, New South Wales. SUBJECTS: Fifty asymptomatic subjects were recruited from the students and staff of the above college. INTERVENTION: Single, unilateral "diversified," high velocity, low amplitude, rotatory thrust technique. MAIN OUTCOME MEASURES: Joint crack sound wave analysis of digital audio tape (DAT) recordings, taken from two skin mounted microphones positioned on either side of the cervical spine. RESULTS: All 50 subjects exhibited at least one audible joint crack sound during manipulation. Forty-seven subjects (94%) exhibited cracking on the ipsilateral side to head rotation (95% confidence interval, 83.5% to 98.7%). One subject exhibited joint cracking on the contralateral side only, while two subjects exhibited bilateral joint crack sounds. There was a statistically significant lower rate of exclusively ipsilateral joint cracking in subjects with a history of neck trauma (80% vs. 100%, p = .023). CONCLUSIONS: This research suggests that during the "diversified" rotatory manipulation of the cervical spine utilized in this study, there is a higher occurrence of the joint crack on the ipsilateral side to head rotation.