The internal oblique is a small, thin, deep muscle of the abdomen. It runs diagonally opposite underneath the external obliques. It has a quadrilateral form which extends from the hip bone (crest of the ileum) to the cartilage of the lower ribs (the seventh, eighth, and ninth ribs). This muscle protects a weak point in the abdominal wall and works with the external oblique to help twist the torso.
