Gas or air bubbles in a joint space are most commonly associated with the "vacuum phenomenon," a collection of gas that has precipitated out of solution to take up a gaseous state within a joint. This phenomenon was unbeknown to us upon a patient presentation, seen on computed tomography scan, and so further academic investigation was performed to define this pathology. Because of this lack of awareness, a PubMed® literature review was performed to analyze the rate of incidence in foot and ankle. Additionally, we present a case example of the vacuum phenomenon in the ankle joint of a 50-year old patient presenting with degenerative ankle joint pain symptoms. Further, a review of the condition as well as differentials is discussed in an attempt to raise awareness of this differential diagnosis for gas bubbles within a joint. [ABSTRACT FROM AUTHOR]