The medial longitudinal arch of the foot acts as a natural shock absorber and spring. A “fallen arch” describes acquired adult flatfoot deformity (AAFD), a progressive condition. It is most commonly caused by the gradual failure of the posterior tibial tendon, a major supporting structure. When this tendon weakens, it can no longer stabilize the foot, leading to the arch collapsing and the foot flattening out. This structural change often results in pain and difficulty with mobility.
Recognizing the Early Physical Symptoms
The earliest and most common sign of an arch problem is a persistent pain felt along the inside of the foot and ankle. This discomfort typically localizes to the area just below the inner ankle bone, which is where the posterior tibial tendon travels. The pain can be described as an aching, throbbing, or sharp sensation that tends to worsen with activity, such as walking, running, or prolonged standing.
Swelling is also a frequent early symptom, often appearing alongside tenderness along the tendon’s path on the inside of the ankle. As the condition advances, the pain may shift to the outside of the ankle as the foot structure changes and the heel tilts outward. Patients often report an increased sense of fatigue in the feet and ankles, especially toward the end of the day or after physical exertion.
A more specific sign of tendon weakness is difficulty or inability to perform a single-leg heel raise. Normally, when you stand on your toes, your heel should invert or roll slightly inward, which helps recreate the arch. If the arch-supporting tendon is failing, trying to stand on the toes of the affected foot will be painful, weak, or impossible, and the heel will remain tilted outward.
Visualizing Changes and Performing Self-Checks
One simple way to check for a collapsed arch is the “wet footprint test,” which requires wetting your feet and stepping onto a surface like paper or cardboard. A normal footprint shows a noticeable inward curve along the arch, with the mid-foot area only partially filled in. A fallen arch, in contrast, leaves a footprint that is almost entirely filled in, showing little to no inward curve where the arch should be.
Another visual indicator is observing the “too many toes” sign, which requires having someone look at your feet from directly behind you while you stand. In a normal foot alignment, only the pinky toe and perhaps a little of the fourth toe are visible from this perspective. If the arch has collapsed, the forefoot often splays out, allowing three or more toes to be seen from the back.
You can also examine the wear pattern on a pair of well-worn shoes. A collapsed arch causes the foot to roll inward excessively (overpronation), placing increased pressure on the inner edge of the foot. This results in excessive wear on the inner sole and heel of the shoe. Additionally, the heel of the affected foot may appear crooked or tilted outward when viewed from behind, a change known as hindfoot valgus.
Common Causes of Arch Collapse
The most frequent cause of an arch collapsing in adulthood is the progressive degeneration of the posterior tibial tendon, which is often a result of cumulative wear and tear. This tendon is subjected to repetitive microtrauma, which can lead to inflammation and failure over time. The condition is often seen in individuals over 40, and women are more susceptible than men.
Excess body weight, or obesity, places a greater load on the foot’s supporting structures, accelerating the strain on the posterior tibial tendon. Repetitive, high-impact activities, such as running or jumping sports, also contribute significantly to overuse of the tendon. Other contributing factors include pre-existing conditions like diabetes, hypertension, and inflammatory disorders such as rheumatoid arthritis, all of which can weaken tendons.
Related Issues in the Body
When the arch collapses, it alters the foot’s mechanics and disrupts the alignment of the entire leg. This leads to a chain reaction of biomechanical problems that travel up the body due to the foot’s excessive inward roll. The inward rotation of the lower leg puts unnatural stress on the knee joint.
Consequently, many people with a fallen arch begin to experience pain in their knees, often on the inner side, due to altered weight distribution and joint stress. This misalignment continues upward, causing the pelvis to tilt and leading to discomfort in the hips and lower back. If these secondary pains or the primary foot symptoms become severe or interfere with daily life, seek a professional medical evaluation.