Medial is a 'position' word, meaning 'on the inner aspect'.
Medial versus lateral
The side of the knees which touch each other are the medial sides, while the outer sides of the knees are the lateral sides. However a structure may be relatively medial to another structure - for example the kneecap is medial to the outer side of the knee.
Anatomical terminology and nomenclature: past, present and highlights. Kachlik D, Baca V, Bozdechova I, Cech P and Musil V. Surg Radiol Anat. 2008 Aug;30(6):459-66. doi: 10.1007/s00276-008-0357-y. Epub 2008 May 17.