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Metatarsalgia

INTRODUCTION

Background

Metatarsalgia is a common overuse injury described as pain in the forefoot associated with increased stress over the metatarsal head region. Metatarsalgia often is referred to as a symptom, rather than as a specific disease. Common causes of metatarsalgia include interdigital neuroma, metatarsophalangeal synovitis, avascular necrosis, sesamoiditis, and inflammatory arthritis; however, these causes often are diagnosed separately.

Frequency

United States

Athletes who participate in high-impact sports involving the lower extremities commonly present with forefoot injuries, including metatarsalgia.

Functional Anatomy

Body weight is transferred by gravity to the foot. This transfer of force is increased to the forefoot during the midstance and push-off phases of walking and running. In the forefoot region, the first and second metatarsal heads receive the greatest amount of this energy transfer. Peak vertical forces reach 275% of body weight during running. A runner may absorb 110 tons per foot while running 1 mile. Pressure studies have shown that runners spend most of the time weighted over the forefoot while running.

Sport Specific Biomechanics

Athletes who take part in high-impact sports involving running or jumping are at high risk of forefoot injury. While track and field runners are exposed to the highest level of traumatic forces to the forefoot, many other athletes, including tennis, football, baseball, and soccer players, often present with forefoot injuries.

CLINICAL

History

The primary symptom of metatarsalgia is pain at one or more of the metatarsal heads. Diffuse forefoot pain and midfoot pain are often present in athletes with combinations of high-impact inflammatory conditions.
Pain typically is aggravated during the midstance and propulsion phases of walking or running.
A history of gradual chronic onset is more common than acute presentation. Chronic symptoms may be of gradual onset over 6 months.
Morton neuroma (interdigital neuroma) produces symptoms of metatarsalgia due to irritation and inflammation of the digital nerve located in the web space between the metatarsal heads. Patients with Morton neuroma may complain of toe numbness, in addition to pain in the forefoot. The term Morton neuroma is a misnomer because no neuroma truly exists. Rather, the lesion results from a mechanical entrapment neuropathy.

Physical

Palpable point tenderness at the distal end of the plantar metatarsal fat pad is a typical finding.
Absence of pain in the interdigital space helps assess for the presence of a neuroma.
Pain and tenderness are experienced on the plantar surface of the metatarsal head, which often is accompanied by the development of a callus formation (plantar keratosis).
Patients with interdigital neuroma have maximal tenderness between the web spaces.
Loss of sensation may be present in adjacent toes.
In patients with interdigital neuromas, pain usually is aggravated by the metatarsal squeeze test.
Compression between the metatarsal heads may produce a painful click, known as a Mulder sign.

Causes

The foot frequently is injured during sports activities.
As in many other overuse syndromes, the condition may be the result of an alteration in normal biomechanics that has caused an abnormal weight distribution among the metatarsal heads.
Persistent stress can lead to chronic irritation and inflammation of the periosteum and adjacent tissues.
The following factors can contribute to excessive localized pressure over the forefoot:
- High level of activity
- Prominent metatarsal heads
- Tight toe extensors
- Weak toe flexors
- Hammertoe deformity
- Hypermobile first ray
- Tight Achilles tendon
- Excessive pronation
Some anatomical conditions may predispose individuals to forefoot problems.
- A high arch with stress to the forefoot, as seen with pes cavus foot type, often causes pain in the metatarsal region.
- Individuals with a Morton toe have a short first metatarsal bone. The normal forefoot balance is disturbed, which results in abnormal subtalar joint pronation. This pronation results in the shift of an increased amount of weight to the second metatarsal.
Hammertoe deformity causes metatarsalgia because the top of the shoe pushes the toe down, depressing the metatarsal heads.
- Toes also share some weight bearing.Hallux valgus may create abnormal foot biomechanics.
- These musculoskeletal problems may contribute to forefoot trauma in athletes.
- Callus is formed as a skin reaction to prolonged pressure, with the skin becoming thickened and hyperkeratotic.