The tibialis posterior is a muscle located in the lower leg, specifically behind the shin bone. It plays a crucial role in supporting the arch of the foot and helps with movements such as walking and running. This muscle is responsible for plantarflexion, which is the action of pointing the toes downward. In addition to its primary functions, the tibialis posterior also assists in stabilizing the ankle and foot during various activities. It is innervated by the tibial nerve and is essential for maintaining proper foot alignment and balance, making it important for overall mobility and athletic performance.