Like the foot, the ankle is a complex structure that allows for a variety of movements while at the same time providing stability and controlling how forces travel between the foot and the rest of the body. Weakness of the ankle complex can contribute to flat feet and overpronation in several ways. Ankle weakness refers to both instability at the ankle joint and impaired strength and coordination of the muscles around the joint.
Movement of the ankle complex comes from two joints:
- The true ankle joint (tibiotalar joint) that allows dorsiflexion and plantar flexion of the ankle.
- The subtalar joint that allows inversion and eversion of the ankle.
These joints are held together by a series of ligaments. Additional stability is provided by the muscles of the lower leg that cross the ankle joint and attach to bones in the foot.
The posterior tibialis muscle starts in the calf and travels down along the inside of the ankle and attaches to the underside of the foot near the arch. One of the main functions of this muscle is maintaining the height of the arch. Weakness in the posterior tibialis muscle is known to be associated with flat feet. Additionally, when the muscle degenerates or ruptures (this commonly happens in older adults) the result is often a completely flat foot.
Even though when it comes to pronation and flat feet it's the posterior tibialis that usually gets the most attention, it's important to remember it doesn't work in isolation. It is only one part of a complex system of muscles, tendons, and ligaments the work as a whole to stabilize the ankle.
Strengthening Weak Ankles
Ankle strengthening can be achieved with resistance exercises that target the muscles around the joint like calf raises and exercises that challenge balance.