Metatarsals

Introduction

Introduction to the Metatarsals

The metatarsals are five miniature long bones that form the skeleton of the forefoot, connecting the tarsus proximally to the phalanges distally. They are numbered 1 to 5 from medial (hallux side) to lateral (little toe side). Together they form the transverse arch of the foot and are essential for weight‑bearing, propulsion, and balance during gait. The metatarsal heads are the main weight‑bearing points on the sole and are common sites of stress fractures, avascular necrosis, and degenerative conditions. Their unique shapes—particularly the robust first metatarsal and the mobile fifth metatarsal—reflect the functional demands of the foot during the stance and push‑off phases of walking.

Study

1. General Features of a Metatarsal Bone

Each metatarsal is a long bone with a proximal base (for articulation with the tarsal bones and adjacent metatarsals), a shaft, and a distal head (for articulation with the proximal phalanx). The bases are wedge‑shaped and interlock to help maintain the transverse arch. The shafts are slender, taper distally, and are convex dorsally. The heads are smooth and rounded, bearing articular cartilage that extends more plantarly, reflecting the need for weight‑bearing during toe‑off. The plantar aspects of the heads have grooves for the long flexor tendons.

2. Individual Metatarsals

First metatarsal: The shortest, thickest, and most medial. Its base has a kidney‑shaped facet articulating with the medial cuneiform. The plantar surface bears a prominent tuberosity for the insertion of the peroneus longus tendon and sometimes the tibialis anterior. The head articulates with the proximal phalanx of the great toe and has two grooves on its plantar aspect for the sesamoid bones of the flexor hallucis brevis tendon. The first metatarsal bears twice the load of the other metatarsals during gait.

Second metatarsal: The longest metatarsal, often the reference for metatarsal length. Its base is recessed and articulates with the intermediate cuneiform and part of the medial and lateral cuneiforms, creating a mortise that locks it in place. This rigid anchorage makes it the keystone of the transverse arch but also the most common site of stress fractures (march fractures).

Third metatarsal: Articulates with the lateral cuneiform and adjacent metatarsals. Its base is similar in shape to the second but smaller.

Fourth metatarsal: Articulates with the cuboid and adjacent metatarsals. Its base is relatively small and mobile.

Fifth metatarsal: The most lateral, distinguished by the styloid process—a large bony prominence projecting proximally from the lateral base. The styloid process receives the insertion of the peroneus brevis tendon. The base also articulates with the cuboid and the fourth metatarsal. The fifth metatarsal is the most mobile metatarsal and is frequently injured.

3. Ossification

Each metatarsal ossifies from two centres: a primary diaphyseal centre (appearing during the 9th–10th weeks of fetal life) and a secondary epiphyseal centre. In metatarsals 2–5, the secondary centre appears at the head (distal) around 3–4 years; in the first metatarsal, the secondary centre appears at the base (proximal) around 2–3 years. An additional secondary centre for the styloid process of the fifth metatarsal appears at about 9–11 years in girls and 11–14 years in boys, fusing by 15–16 years. This epiphysis is often confused with a fracture. The epiphyses fuse around 17–20 years.

4. Clinical Considerations

Metatarsal fractures are common and classified by location: head, neck, shaft, or base. The Jones fracture is a transverse fracture at the base of the fifth metatarsal, at the junction of the diaphysis and metaphysis (within 1.5 cm of the styloid tip). It has a high rate of non‑union due to poor blood supply at this watershed zone. An avulsion fracture of the styloid process (pseudo‑Jones fracture) is caused by the peroneus brevis tendon pulling off the tip. March fractures are stress fractures, most commonly of the second or third metatarsal shafts, from repetitive loading. Freiberg's disease is an avascular necrosis of a metatarsal head, typically the second or third, presenting in adolescent females. Metatarsus adductus is a congenital forefoot adduction deformity. Hallux valgus involves medial deviation of the first metatarsal with lateral deviation of the great toe, often with an inflamed bunion over the medial eminence.

Summary

Summary of the Metatarsals

The five metatarsals form the forefoot skeleton, articulating with the tarsals proximally and phalanges distally. The first metatarsal is thick and bears the most weight; the second is the longest and most rigid; the fifth bears the prominent styloid process for peroneus brevis insertion. Ossification patterns differ between the first and the lateral four metatarsals. Common clinical conditions include fractures (Jones, march, avulsion), Freiberg's disease, and hallux valgus.