Pain in the foot that occurs specifically when walking can often be traced to the Flexor Hallucis Brevis (FHB), a small yet powerful muscle located deep in the sole of the foot. The FHB plays a large part in foot function during movement. Pain here is common for active individuals, and it becomes most noticeable during the weight-bearing phases of walking or running. Understanding the role of the FHB and the common causes of its irritation is the first step toward finding relief.
Understanding the Flexor Hallucis Brevis Muscle
The Flexor Hallucis Brevis is an intrinsic foot muscle, contained entirely within the foot, and positioned directly beneath the first metatarsal bone. The muscle’s two main tendons house the sesamoid bones, which are two small, pea-shaped bones. The sesamoids act like a pulley system, increasing the mechanical advantage of the FHB muscle.
The primary job of the FHB is to flex the big toe at the metatarsophalangeal (MTP) joint, where the toe meets the foot. This movement is integral to proper gait mechanics. As the body moves forward during walking, the FHB stabilizes the big toe and the foot’s medial arch.
The muscle’s function is most noticeable during the “push-off” phase of a step. It anchors the big toe to the ground, providing the final lever action needed to propel the body forward. When the FHB is compromised, this push-off phase becomes painful, which is why walking is a common trigger for discomfort.
Why This Muscle Causes Pain When Walking
Pain in the area of the FHB is related to excessive strain or compression, with the most common culprits being tendinopathy and sesamoiditis. Flexor Hallucis Brevis tendinopathy involves inflammation or degeneration of the tendon itself, resulting from repetitive microtrauma. This overuse injury often occurs following a sudden increase in activity or a change in footwear that places greater load on the forefoot.
Sesamoiditis is an inflammatory condition affecting the two tiny sesamoid bones and the surrounding tissue embedded within the FHB tendon. Because these bones absorb significant impact force during the push-off of walking, they are susceptible to irritation. The pain from sesamoiditis is sharp and localized directly beneath the ball of the foot, under the big toe joint.
The mechanism of injury is often linked to biomechanical issues, such as a foot structure with a high arch or an excessively rigid first ray, which increases pressure on the sesamoids. Footwear that lacks cushioning or has a high heel can also contribute to mechanical overload on the area.
An acute cause of FHB pain is “Turf Toe,” a hyperextension sprain of the big toe joint that often tears or strains the FHB tendon and capsule. In all these cases, pain manifests most intensely during weight-bearing, particularly when the foot is maximally dorsiflexed just before the toe leaves the ground.
Treatment Strategies for Recovery
Initial management of FHB pain focuses on reducing inflammation and offloading the injured structures. The RICE protocol (Rest, Ice, Compression, and Elevation) remains the standard first step to calm acute symptoms. Applying ice to the ball of the foot for about 15 minutes several times a day helps reduce local swelling and pain.
Mechanical adjustments are a major part of recovery, minimizing the pressure on the painful area during walking. Wearing stiff-soled shoes or a specialized walking boot limits motion at the big toe joint, preventing painful hyperextension. Orthotics with a metatarsal pad or a specific cut-out beneath the sesamoids can redistribute weight away from the injured area.
Once the initial pain subsides, rehabilitation transitions to restoring strength and flexibility to the foot musculature. Targeted exercises, such as “towel scrunches” where the toes gather a towel on the floor, help strengthen the intrinsic foot muscles including the FHB. Another effective exercise involves isolating and pressing the big toe into the ground while lifting the four smaller toes, which directly works the FHB.
Gentle stretching of the big toe joint is necessary to maintain mobility, but must be done cautiously to avoid re-irritating the tendon or sesamoids. A common stretch involves pulling the big toe back toward the ankle until a mild stretch is felt under the foot, holding for 15 to 30 seconds. A gradual return to full activity is essential, ensuring that increased walking distance or intensity does not cause a return of symptoms.