The Pellegrini-Stieda lesion is a common finding on conventional X-rays. Whether it originates in the medial collateral ligament (MCL) of the knee or the medial head of the gastrocnemius muscle or another structure remains under debate. We discuss the difference in the articles by Pellegrini and Stieda and follow the vision on the origin of the lesion through time. A systematic research in PubMed/MEDLINE was conducted, identifying all articles on the Pellegrini-Stieda lesion and analyzing them for proposed origin of the lesion. The articles with their conclusion based on either finding during surgery or magnetic resonance imaging (MRI)/computed tomography were analyzed in more detail. Our PubMed/Medline search identified 4,997 articles. After exclusion of articles that were not on the Pellegrini-Stieda lesion and of doubles, 27 articles remained. By checking the references manually, 10 more articles were identified. Proposed origins were MCL, medial gastrocnemius, adductor magnus, vastus medialis, deep MCL, and superficial MCL. Although the MCL was most often coined as origin of the lesion (54% overall, 25% on MRI, and 57% during surgery), many cases remained undecided (50% on MRI) or no specific structure was found to be the origin (29% during surgery). There are diverse proposed origins of a calcification on the medial side of the knee. The eponymous term Pellegrini-Stieda lesion seems fitting, as it comprises two different thoughts on the origin of the lesion. MRI seems to be a noninvasive and quite accurate method for future research.