Biomechanics of the posterior oblique ligament of the knee

•The posterior oblique ligament is anatomically and functionally distinct from the superficial medial collateral ligament.•The posterior oblique ligamen tplays a key role to posterior tibial translation in posterior cruciate-deficient knee.•The posterior oblique ligament is the main stabiliser against internal rotation in early flexion angles.•The posterior oblique ligamentbears up to 47% of the force borne by the anterior cruciate ligament in internal rotation.