Pain Under the Medial Arch of the Foot

Question: If a person experiences pain under the medial arch of the foot while walking or while rising onto the balls of the feet to reach for something, which structure is likely to be injured?

Answer: The flexor hallucis. The flexor hallucis is a very strong muscle-tendon unit that takes the lion's share of our weight while we walk, stand and rise onto the balls of our feet. The muscle is located in the calf, and its tendon begins just medial to the Achilles' tendon. The tendon passes under the medial heel and travels along the medial arch of the foot to attach distally at the great toe.

Poor alignment makes the flexor hallucis tendon more susceptible to injury. In a normally aligned foot, roughly one-third of the body's weight falls onto the great toe, with one-sixth falling onto each of the other toes. If the feet are turned out while standing and walking, even more weight falls onto the great toe - and therefore onto its flexor tendon. In such cases, strain or tendinitis of the flexor hallucis tendon is fairly common. In cases where poor alignment is placing pressure on the medial arch, there often is a callus at the medial edge of the great toe and/or the medial aspect of great toe joint.

Flexor hallucis injuries occur most commonly in the medial arch of the foot. Injuries to the flexor hallucis tendon at the back of the ankle, where the tendon is running parallel to the Achilles', are sometimes mistaken for Achilles' tendinitis. Injuries to this tendon near the anterior portion of the heel often are mistaken for plantar fasciitis. If a person feels pain not just at the medial arch, but in a wider area under the arch of the foot, this might indicate that the flexor tendons of several other toes also are strained or that a plantar fasciitis is present.

Question: What assessment test would you perform to verify this injury?

Answer: Resisted plantar flexion of the great toe.

First, hold the great toe in slight dorsiflexion (Figure 1) with your thumb and ask the person to push the toe down against you (into plantar flexion). If the injury is relatively severe, this test will be positive (causing a little pain). If the tendon is only mildly strained, you'll need to perform one or two additional tests to place more stress on the tendon.

The second test is performed in a standing position. While holding the client's hands for balance, ask the person to rise onto the balls of the feet (Figure 2). If this reproduces the person's pain, and the pain is in the medial arch, you have confirmed the presence of flexor hallucis tendon strain. If the reproduced pain is in the Achilles' area, you'll need to do further testing to determine whether it's coming from the Achilles' or the flexor hallucis. If this second test does not cause discomfort, move on to the third test.

For this final test, have the client face a wall and lean against it at approximately a 35-degree angle, while rising up onto the balls of the feet (Figure 3). If this causes no pain or discomfort in the offending area, ask the person to transfer most of his or her weight onto the big toes. This places maximum stress on the flexor hallucis tendon.