The foot is a complex structure of bones, joints, and soft tissues that supports the entire weight of the body. While the bottom of the foot is known as the sole or plantar surface, the correct name for the top is often unknown. Understanding the anatomy of this area is important for recognizing its role in movement and identifying the source of common discomforts. This guide clarifies the proper anatomical terms and explores the structures and issues associated with the top of the foot.
The Correct Anatomical Terminology
The official anatomical name for the top surface of the foot is the Dorsum of the Foot, or Dorsum Pedis. This term derives from the Latin word dorsum, meaning “back,” and is used in anatomy to describe the upper surface of any body part. The opposite side, the bottom of the foot, is known as the plantar surface.
The term Instep is often used conversationally to describe the top of the foot, but it is not interchangeable with dorsum. The instep technically refers to the highly arched, prominent central section of the dorsum. This bony prominence is formed by the tarsal and metatarsal bones.
The dorsum encompasses the entire upper region, extending from the ankle joint down to the toes. Using the correct term provides precision when communicating with healthcare professionals about symptoms or injuries. The dorsal side of the foot is also characterized by thin skin, which makes underlying structures easily visible.
Major Bones and Tendons of the Dorsum
The architecture of the dorsum is defined by the distal ends of the tarsal bones and the five long metatarsal bones. These metatarsals form the forefoot, connecting the midfoot to the toe bones, called the phalanges. The dorsum also features small joints and ligaments that provide stability to the foot’s arch.
The thin skin and minimal muscle cushioning mean that these tendons and bones lie close to the surface. This superficial position allows for the easy palpation of the Dorsalis Pedis Artery, which supplies blood to the area. The positioning of these structures is efficient for movement but leaves them exposed to external pressure and injury.
Prominently visible across the top of the foot are the extensor tendons, which lift the foot and toes. The Extensor Digitorum Longus and the Extensor Hallucis Longus are two major tendons that run from the lower leg across the ankle. These tendons facilitate dorsiflexion, the action of pulling the foot upward toward the shin, which is necessary for clearing the ground while walking.
Common Causes of Pain and Swelling
The dorsum is a common site for pain and inflammation due to its superficial tendons, bones, and nerves. One frequent issue is Extensor Tendonitis, which occurs when the extensor tendons become inflamed. This is often due to overuse from activities like running or from wearing shoes that are too tight across the top of the foot. This condition causes a dull ache or tenderness that worsens with activity or when trying to lift the toes.
Another common source of discomfort is a Metatarsal Stress Fracture, which involves tiny cracks in the metatarsal bones. Repetitive impact, such as from long-distance running or a sudden increase in physical activity, can cause these fractures. The pain from a stress fracture is localized, intensifies with weight-bearing, and may be accompanied by swelling.
Localized swelling, or edema, on the dorsum can also be a sign of underlying issues, including arthritis or conditions like gout, which often affects the big toe joint. The confined space around the bones and tendons means that slight swelling can lead to pressure on nerves, causing symptoms like tingling or numbness in the area.