A Dropped Arch

By Ben Benjamin, PhD

Question: What causes the arch of the foot to drop in a pronated position?

Answer: Laxity in the four medial ankle ligaments.

Excess pronation is caused by laxity in the four medial ankle ligaments, called the deltoid ligaments, which hold the bones of the ankle in place.

Over time, excess pronation can cause serious problems. More of the body's weight falls onto the medial side of the foot and the medial knee, which places greater stress on the entire medial aspect of the leg - not just the deltoid ligaments, but also the posterior tibialis muscle tendon unit, the medial portion of the patella tendon, the medial collateral ligament of the knee, and the adductors muscles of the thigh. As a result, these structures constantly are vulnerable to strain and injury. Moreover, excess pronation causes the muscles on the medial portion of the foot, lower leg and thigh to work harder, often straining, while those on the lateral portion do not work enough and begin to weaken and atrophy. Eventually, the entire leg becomes unbalanced and unstable, and injury often results.

When you encounter a client with a dropped arch in a pronated position, refer the person to a good podiatrist who can do a gate analysis and make corrective orthotic devices to support the medial arch of the foot.