Pain in the ball of the foot, particularly under the big toe, often signals an issue with the Flexor Hallucis Brevis (FHB) muscle complex. The FHB is a small but powerful muscle located deep within the sole of the foot. When walking, this muscle is heavily involved in the final phase of the gait cycle, meaning irritation or injury can make simple movements very painful. This article explores the anatomy of the muscle, the primary causes of its pain, and details both immediate and professional strategies for recovery.
Function and Location of the Muscle
The Flexor Hallucis Brevis is an intrinsic foot muscle, meaning it is contained entirely within the foot structure. It originates from the plantar surfaces of the cuboid and cuneiform bones in the midfoot. The muscle splits into two distinct tendons that insert at the base of the big toe’s proximal phalanx.
The primary action of the FHB is to flex the big toe at the metatarsophalangeal joint. For walking, the FHB assists in stabilizing the medial longitudinal arch of the foot. It provides the necessary power for the “toe-off” phase of gait, pushing the body forward with each step.
Two small sesamoid bones are embedded within the FHB tendons directly beneath the first metatarsal head. These sesamoids act as a pulley system, increasing the leverage of the FHB muscle to maximize force during push-off. Due to their location, the sesamoids and surrounding tendons bear significant compressive force with every step, making the complex highly susceptible to injury.
Primary Causes of Flexor Hallucis Brevis Pain
Pain that intensifies during walking, particularly during the push-off phase, stems from three main conditions affecting the FHB complex.
FHB Tendinopathy
FHB Tendinopathy is a chronic strain of the tendon tissue caused by repetitive microtrauma. This often results from activities requiring constant forefoot loading, such as running, dancing, or wearing unsupportive footwear that places excessive stress on the big toe joint.
Sesamoiditis
Sesamoiditis is the inflammation of the two sesamoid bones and the surrounding tissue. Repetitive stress from high-impact activities or walking in high-heeled shoes can lead to this irritation, causing a deep ache in the ball of the foot. Since the sesamoids are embedded within the FHB tendons, their inflammation directly impairs muscle function and causes sharp pain when the toe is extended.
Acute Trauma
Acute trauma can also injure the FHB, often resulting from a sudden, forceful upward bending of the big toe, sometimes referred to as “turf toe.” This mechanism can strain or tear the FHB tendon or even fracture one of the sesamoid bones.
Immediate Strategies for Managing Pain
Managing FHB-related pain begins with immediate activity modification to reduce mechanical stress. Temporarily stop high-impact activities like running or jumping and limit prolonged walking. Rest is crucial for the initial healing process.
Apply ice to the ball of the foot for 15 to 20 minutes several times a day to manage inflammation and reduce localized pain. Choose supportive footwear with a stiff sole or a rocker-bottom design, which reduces the need for the big toe to bend during walking. Padding or taping the area to offload pressure from the sesamoid bones can also provide immediate relief.
Professional Diagnosis and Treatment Paths
Diagnosis begins with a thorough physical examination, including tests for range of motion and big toe strength. The provider will palpate the area to pinpoint tenderness, helping distinguish between tendon, bone, and joint issues. Imaging is utilized to confirm the exact nature of the injury and rule out serious problems.
An X-ray is performed first to check for a sesamoid fracture or other bone abnormalities. If soft tissue damage like tendinopathy or a partial tear is suspected, an ultrasound or Magnetic Resonance Imaging (MRI) scan provides detailed images of the FHB tendon and surrounding structures. Identifying the injured structure accurately is necessary for effective treatment planning.
Treatment for FHB pain is primarily conservative, often starting with custom orthotics or arch supports to correct faulty foot mechanics and redistribute pressure away from the injured area. Physical therapy focuses on restoring strength and flexibility, strengthening the FHB and other intrinsic foot muscles while stretching the calf to reduce forefoot strain. Non-steroidal anti-inflammatory drugs (NSAIDs) may be recommended to manage pain and swelling.
For persistent inflammation, a corticosteroid injection may be considered, but only after a fracture has been ruled out, as steroids can complicate bone healing. Surgical intervention, such as removing a severely fragmented sesamoid bone, is reserved as a last resort for chronic cases that fail to respond to conservative care.