The human foot is a complex structure of bones, joints, and soft tissues that supports the body’s weight and facilitates movement. This foundation is under constant stress, making its anatomy important for understanding mobility and common physical complaints. The framework of the foot is composed of 26 bones, and five of these, known as the metatarsals, form the foundation of the forefoot. These long bones are integral to converting the downward force of standing into the forward push of walking and running.
The Metatarsals: Location and Numbering
The metatarsal bones are situated in the middle region of the foot, acting as a bridge between the rear and forefoot. They are positioned between the tarsal bones (ankle and midfoot) and the phalanges (bones of the toes). There are five metatarsals in each foot, identified using Roman numerals I to V, starting on the medial side with the great toe.
The first metatarsal connects to the big toe, while the fifth metatarsal leads to the little toe, creating a fan-like arrangement across the width of the foot. Each of these long bones consists of three distinct parts: the base (proximal end), the shaft (middle section), and the head (distal end). The head forms the prominent ball of the foot and articulates with the proximal phalanx of the corresponding toe, forming the metatarsophalangeal joint.
Essential Role in Foot Function
The metatarsals distribute the body’s weight across the foot during standing and dynamic activities. They are a major weight-bearing area, particularly at their heads. The first metatarsal is noticeably shorter and wider than the others, bearing approximately 30 to 50% of the force during the gait cycle.
The metatarsals contribute to the foot’s arched structure, supporting both the longitudinal and transverse arches. While the arches absorb shock and provide flexibility, the metatarsals must also act as a rigid lever during the final phase of walking. As the heel lifts off the ground, they convert the foot into a firm platform for propulsion, enabling the push-off that drives the body forward.
Common Conditions Involving the Metatarsals
The constant forces placed upon these bones make them susceptible to various overuse and trauma-related conditions. One of the most frequently encountered issues is Metatarsalgia, a general term for pain and inflammation that occurs in the ball of the foot. This discomfort is often traced to the metatarsal heads, where excessive pressure or misalignment can cause irritation of the surrounding tissues.
Repetitive stress from activities like running or marching can lead to a hairline break known as a stress fracture. These fractures most commonly occur in the second or third metatarsals due to their relatively fixed position and length, subjecting them to high impact forces. Acute fractures are also common, with the fifth metatarsal being a frequent site of injury, often sustained from twisting the ankle or direct impact. Structural issues, such as misalignment, can also alter pressure distribution and contribute to chronic pain.