When the arches of the feet collapse, a lot of bad things happen. First, consider that the arch of the foot is supposed to flex and absorb shock. If the arch is flat, the foot lacks shock absorbency, and stress is transferred to the knees, hips, and lower back. This is why many of the advertisements for orthotics claim that they can resolve back pain.

With fallen arches, the bones of the ankle are not optimally aligned with the foot, increasing the risk of ankle injuries. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, approximately one million people in the US are treated for ankle injuries every year. It’s also estimated that athletes who injure an ankle are five times more likely to injure that ankle again.

Fallen arches also cause the bones of both the upper legs and lower legs to internally rotate. This rotation increases stress on the ACL. The ACL is a ligament that connects the upper and lower leg bones and provides stability to the knee, making the ACL critical for dynamic movements. Approximately 300,000 ACL injuries occur annually in the US, and the risk of injury is greater to athletes and women. Also consider that only 30 percent of ACL injuries are a result of direct contact, which suggests that an important step to preventing ACL injuries is to address the structure and function of the foot.

Another consequence of fallen arches is that the inward rotation of the upper legs increases the arch in the lower back, a condition technically referred to as lumbar hyperlordosis. Lumber hyperlordosis reduces the ability of the spine to absorb shock. The result is an increased risk of back injury and pain.

The most common method of correcting flat feet is orthotics. Orthotics don’t permanently correct fallen arches – they only work while the user is wearing them. Also, the pressure of the orthotic on the arch can also cause the arch to become weaker.

Solutions include corrective exercises to strengthen muscles that support the arch. One such muscle is the extensor hallucis longus, which creates lateral tension on the foot and also strengthens and stretches the two major calf muscles (gastrocnemius and soleus).