The calcaneus, commonly known as the heel bone, is a key component of the human foot. It supports body weight and enables movement. This bone connects various structures, allowing for the foot’s complex functions.
Anatomy of the Calcaneus
The calcaneus is the largest bone in the foot, forming the heel. It is one of the seven tarsal bones. This bone has an irregular, roughly cuboidal shape, with its long axis pointing forward and laterally.
It articulates with the talus, directly above it, and the cuboid, in front of it. These form the subtalar and calcaneocuboid joints, which are vital for foot movement. The calcaneus features multiple surfaces, including a large posterior tuberosity where the Achilles tendon attaches. Internally, it has a spongy, cancellous bone structure encased by a harder outer shell.
Primary Functions of the Calcaneus
The calcaneus plays a role in several mechanical functions of the foot, primarily weight bearing. It transfers the majority of the body’s weight from the lower leg to the ground, acting as a direct contact point during standing and locomotion. Its robust design allows it to support the entire body weight, making it a significant load-bearing bone.
This bone is also instrumental in shock absorption, a function enabled by its internal spongy structure and the surrounding fat pad. When the heel strikes the ground during walking or running, the calcaneus, along with the fat pad, helps to cushion the impact and distribute forces evenly, protecting the joints further up the leg. Additionally, the calcaneus acts as a lever for the powerful calf muscles, particularly the gastrocnemius and soleus, which insert onto its posterior surface via the Achilles tendon. This connection is vital for plantar flexion, the downward movement of the foot, which generates the propulsion needed for walking, running, and jumping.
Common Calcaneal Injuries and Conditions
Despite its strength, the calcaneus is susceptible to various injuries and conditions, often due to the high forces it endures. Calcaneal fractures are breaks in the heel bone that typically result from high-impact events, such as falls from a height or motor vehicle collisions. These fractures can cause severe pain, bruising, swelling, and difficulty bearing weight or walking. The bone’s internal structure means that high-impact fractures can cause the calcaneus to shatter and become fragmented, making treatment complex.
Heel spurs are another common condition involving the calcaneus, characterized by bony outgrowths on the underside of the heel bone. These spurs form from calcium deposits, often developing over time due to long-term stress on the muscles and ligaments of the foot. While some heel spurs are painless, they can cause significant discomfort, particularly when associated with inflammation of the surrounding tissues, such as the plantar fascia.
Plantar fasciitis is an inflammation of the plantar fascia, a thick band of tissue that connects the calcaneus to the toes, supporting the arch of the foot. This condition commonly causes stabbing pain near the heel, often worse with the first steps in the morning or after periods of rest. It can be related to overuse, inadequate foot support, or excessive pressure on the plantar fascia.