The vastus medialis, also known as the teardrop muscle, is a muscle on the inner side of the thigh that is important for knee extension and stability. There are a few different synonyms for this muscle that you might come across in anatomy or fitness literature. Some common alternatives include the vastus internus, vastus medialis oblique (VMO), and medial quadriceps. The vastus internus is the Latin term for the muscle, and the VMO is a more specific term that refers to the upper portion of the vastus medialis that helps stabilize the patella (kneecap). The medial quadriceps is another name that emphasizes the muscle's location on the inner side of the thigh.