The counterclaim to Roston and Haines’ interpretation came from a trio named Unsworth, Dowson and Wright in 1971. Much like the previous pair, they used a similar procedure to confirm the inner workings of the joints. However, the three came to a very different conclusion. For them, the cracking sound was the result of the collapse of the bubble between the joints, not its formation.
Since that study over 40 years ago, both interpretations have been used in publications on the matter, proving the scientific divide. However, the knuckle-cracking debate took another turn in April 2015, as a number of scientists took a closer look at the issue. Surprisingly, the inspiration came from an unexpected source.
Working as a professor of radiology at the University of California, Robert Boutin decided to kick-start the research on joint-cracking thanks to his 11-year-old daughter. Her curiosity on the matter inspired him to begin a new study, but the overall divisiveness of the debate also played a big role.