Calcaneofibular ligament

The calcaneofibular ligament starts at the tip of the lateral malleolus, the bony prominence at the end of the fibula (the rounded bone on the outside of the ankle). It runs downward and backward to attach to the outer surface of the heel bone (calcaneus). In its Korean name, “jong” refers to the heel bone (calcaneus), and “bi” refers to the fibula, meaning that it connects these two bones. Its plain-language Korean name means “heel–fibula ligament.”

There are three ligaments on the outside of the ankle. The Anterior talofibular ligament, posterior talofibular ligament, and calcaneofibular ligament make up the Lateral ankle ligaments. Two features distinguish the calcaneofibular ligament.

• It crosses two joints. It passes across both the Talocrural joint (ankle), which connects the fibula and the talus, and the Subtalar joint (hindfoot) below it.
• It passes beneath the tendons on the outside of the lower leg. It runs just beneath the tendons of the Fibularis longus and brevis, which descend from the outside of the lower leg into the foot.

Its job is to keep the foot from turning too far inward (Inversion and eversion). It plays a particularly important role in controlling this movement when the ankle is in a neutral position or bent upward toward the top of the foot. Like a strap attached to a door hinge, it stays quiet at rest, then tightens as the foot tilts inward to prevent excessive movement. However, ankle stability does not depend on this ligament alone. It results from the combined contributions of the shape of the hindfoot joints, other ligaments, the capsules surrounding the joints, the responses of the lower-leg muscles, and the ground surface.

A lateral ankle sprain, in which the ankle rolls inward, is the most common ankle injury in sports and everyday life. Usually, the anterior talofibular ligament at the front is stretched first. If the ankle rolls farther, or if its angle is different, the calcaneofibular ligament may also be stretched or injured. Immediately after a sprain, the outside of the ankle becomes swollen and bruised, and bearing weight is uncomfortable. The exact proportion of injuries involving only the calcaneofibular ligament varies across studies, so it is difficult to give a single definitive figure.

• For several days after a sprain, the area running from the outside of the ankle toward the heel is swollen and painful.
• Even a few weeks later, the ankle may sometimes feel unstable on uneven paths or downhill slopes.
• When you feel your ankle tilting inward, you instinctively tense your muscles.

Discomfort on the outside of the ankle can arise in similar ways from tendons, joint capsules, and tissues around the bones, as well as from ligaments. It is therefore difficult to identify which ligament is injured based on the location of pain alone.

Ultrasound and MRI show whether the calcaneofibular ligament remains continuous, how thick it is, and the condition of the surrounding tissues. However, ligament changes seen on imaging do not always match the degree of pain or instability a person actually feels. In clinical practice, imaging findings are therefore considered together with a hands-on assessment of ankle movement, whether there is a feeling of instability, and how these findings change over time.

• Immediately after a sprain — If bearing weight is uncomfortable, avoid pushing yourself, keep the ankle elevated, and use a cold compress to reduce swelling. If the pain is severe or even standing is difficult, it is a good idea to have it checked at a hospital.
• Regaining movement — Once the swelling subsides, try starting with gentle up-and-down ankle movements.
• Balance practice — Standing on one leg is a common way to wake up the sensory receptors within ligaments. Start by holding onto a wall, then try closing your eyes or standing on an unstable surface. See Balance training and Proprioception.
• Strengthening the muscles on the outside of the lower leg — Looping a band around the outside of the foot and slowly turning it outward helps strengthen the ability of the outer lower-leg muscles to support the ankle.
• Repeated sprains — If you keep spraining the same ankle, also read Chronic ankle instability.