Which structure does the flexor hallucis longus NOT pass under?

The flexor hallucis longus is a muscle located in the posterior compartment of the leg, primarily responsible for flexing the great toe, as well as assisting with ankle plantarflexion and foot supination. This muscle travels down the leg, passes behind the medial malleolus, and crosses under the sustentaculum tali, navicular, and talus as it approaches the foot's arch before attaching to the base of the distal phalanx of the big toe.

The cuboid bone, however, is not a structure that the flexor hallucis longus passes under. Instead, it is situated more laterally in the foot and does not directly engage with the path of the flexor hallucis longus tendon. The tendon typically runs along the plantar aspect of the foot, passing beneath the navicular and various tarsal bones, but it does not need to pass beneath the cuboid since its course is more medial. This characteristic is crucial for understanding the anatomy and biomechanics of the foot and can help in assessing conditions affecting the flexor hallucis longus or related structures.