Knuckle cracking refers to the characteristic sound produced when joints are moved or distracted, and there is considerable interest in the mechanism and the clinical associations of knuckle cracking. Different mechanisms for knuckle cracking have been proposed over a century, and some have speculated that it can lead to deleterious effects on the joints. Herein, we review the literature on the mechanism and clinical associations of knuckle cracking. There is agreement in the literature regarding the formation of a bubble as part of the mechanism of knuckle cracking; however, the process by which the bubble is formed and the source of the cracking sound is not clear. The evidence for the association of knuckle cracking and osteoarthritis comes mainly from observational studies that have failed to show an association. Fewer studies report other associations mainly through descriptive, small or cross-sectional studies. Clin. Anat. 31:942-945, 2018. © 2018 Wiley Periodicals, Inc.