The effect of adenomyosis on reproduction can only be determined if there are clear definitions of this disease entity. Adenomyosis should be distinct from endometriosis rather than regarded as a subclassification. The diagnosis of adenomyosis should employ standard criteria that are accessible, replicable, noninvasive, and cost-effective. The Morphological Uterus Sonographic Assessment (MUSA) is a standard and validated system to diagnose adenomyosis. However, not all markers in the MUSA correlate with clinically relevant outcomes. Analysis of outcomes according to each individual sonographic marker may be the key to correctly identifying significant phenotypes of adenomyosis and evaluating its true impact on reproduction.