Calcaneus (Heel Bone)

What is the Calcaneum Bone

Calcaneum also known as the heel bone, is an irregularly-shaped, short, cuboidal bone situated in the hindfoot, just below the ankle. It is the largest tarsal, as well as the largest foot bone that forms the prominence of the heel. It is a weight-bearing bone, supporting the entire body weight while standing or walking.

The term ‘calcaneum’ is derived from the Latin word ‘calcaneum‘, meaning ‘heel’.

Where is the Calcaneum Located

Calcaneum is situated in the hind region of the foot, specifically in the heel region. More precisely, it lies below the three bones, the talus, tibia, and fibula, that make up the ankle joint. Whenever you touch your heel, you can feel the calcaneum.

Calcaneum Facts

Functions

• Bear the body weight while walking or standing.
• Transfer most of the body weight from the leg to the foot.
• Act as a lever for the calf muscles.

Anatomy – Parts and Bony Landmarks of the Calcaneum

As mentioned, the calcaneum is an irregular cuboid bone whose superior surface can be divided into three areas – the posterior, middle, and anterior regions.

1. Posterior Region

The posterior part of the calcaneum is large, rough, convex, and dome-shaped. The Achilles or calcaneal tendon gets inserted on the superior side of the posterior part. Internally and externally, there are two bursae(fluid-filled sacs) in the front and back of this insertion point, that act as cushions. The convexity of the posterior part supports the Kager’s fat pad, the fibroadipose tissue between the calcaneal tendon and the ankle joint. This part also features a thickened landmark called the calcaneal tuberosity that provides the origin site for the abductor digiti minimi and abductor hallucis. The tuberosity bears the medial and lateral processes.

2. Middle Region

The middle part bears three articular surfaces: the anterior talar articular surface, the middle talar articular surface, and, the largest, the posterior talar articular surface. The calcaneum articulates superiorly with its adjacent tarsal bone talus through these three surfaces. A rough depression, called the calcaneal sulcus or sulcus calcanei, narrows into a groove connecting the sinus tarsi with the talus on the medial side. On the lateral side of the calcaneum, a tubercle known as the peroneal or calcaneal tubercle is present.

3. Anterior Region

The front of the calcaneum, the part lying on the side of the toes, is roughly triangular.  It bears a saddle-shaped articular surface that articulates with another tarsal bone, the cuboid. A horizontal shelf-like structure arises on the anteromedial portion of the bone, called the sustentaculum tali.

Development and Ossification

The calcaneum develops from two ossification centers: one primary and another secondary. The primary center starts to form during the 3rd month of the gestational period, and the other one usually after age 8. The entire process of ossification gets completed by the age of 15.

Joints and Articulations

1. Talocalcaneal or Subtalar Joint: A synovial joint, formed betweencalcaneum and talus.

2. Calcaneocuboid Joint: Another synovial joint present between calcaneum and cuboid.

Muscle and Ligament Attachments

Being the largest foot bone, the calcaneum provides a large surface area for the complex attachment of the following muscles:

1. Triceps surae (gastrocnemius and soleus) : Gets inserted in the calcaneal tubercle through the calcaneal tendon
2. Abductor halluces: Originates from the medial process of the calcaneal tuberosity.
3. Flexor digitorum brevis: Originates from the medial process of calcaneal tuberosity.
4. Quadratus plantae: Originates from the plantar surface of the calcaneum.
5. Abductor digiti minimi: Originates from the medial and lateral process of the calcaneal tuberosity.
6. Extensor digitorum brevis: Originates from the dorsolateral surface of the bone.
7. Extensor hallucis brevis: Originates from the sinus tarsi.

Identification of Left and Right Calcaneum

A simple way to identify the left and right calcaneum is as follows:

First, hold or place the bone in a way so that the superior convex surface is up. In this position, the smooth anterior surface would be on the outer side, and the posterior surface, i.e., the side of the heel, would be on your side.

Carefully look for the bony projection on the medial side, the sustentaculum tali.  If it lies to the left, it is the right calcaneum and vice versa.

References

1. 1. Calcaneum – Radiopaedia.org
   2. Calcaneum – Kenhub.com
   3. Calcaneum – Healthline.com
   4. Calcaneum – Sciencedirect.com