(Golden Oldie) Let’s get a hand on this: review of the clinical anatomy of “knuckle cracking”

Key Points

1. There is currently a popular belief that knuckle cracking is harmful to the metacarpophalangeal joints as it can lead to osteoarthritis.

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BACKGROUND & OBJECTIVE

Knuckle or metacarpophalangeal (MCP) joint ‘cracking’ is a familiar phenomenon that has gained the interest of researchers and the public. Manipulation of the joint, either through regular movement or when applying a pulling force, can produce a cracking sound. Many joints produce a sound, but not all joints exhibit the characteristic cracking sound. This sound has interestingly been described in the literature as a: crack, pop, clunk, click, crepitus, or snap (1).

Most of the studies on joint cracking are on the MCP joints (2,3). The MCP is a synovial joint composed of a cavity filled with connective tissue (the synovial fluid) between the joint surfaces. In a recent study, Demoulin et al. examined the beliefs of a sample population regarding the origin of cracking sounds during spinal manipulation and found that 9% of participants were aware of what is clinically deemed as the correct mechanism (4). With such an audible noise it is potentially logical to theorize that it can lead to some form of damage, however, this could therefore be said for therapies that manipulate joints.

This paper sought to review the clinical anatomy of knuckle cracking and what causes the sound when knuckle cracking occurs.

Manipulation of the joint, either through regular movement or when applying a pulling force, can produce a cracking sound.

There is currently no agreement in the literature on the origin of the knuckle cracking sound.

METHODS

• This study was a review of current available literature, although no methodology was provided on how the literature was identified.

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