Inversion and eversion

These movements are named according to the direction the sole faces.

• Inversion — A movement that lowers the outer edge of the foot so the sole faces toward the inside of the body. It is similar to turning the soles of both feet to face each other.
• Eversion — A movement that lowers the inner edge of the foot so the sole faces toward the outside of the body.

Sit in a chair, lift your foot slightly off the floor, and turn the sole inward. This is inversion. Turning it outward is eversion. Inversion usually has a greater range of motion than eversion.

Inversion and eversion result from several small joints in the hindfoot and midfoot moving together, including the joint just below the talus. While the ankle joint mainly moves the foot up and down, these joints below it tilt the foot from side to side. Inversion and eversion are therefore complex movements involving the whole foot, rather than movements of the ankle alone.

Different muscles produce these movements. Muscles running along the inner side of the shin (tibialis posterior and tibialis anterior) tilt the foot inward, while muscles on the outer side of the lower leg (fibularis longus and fibularis brevis) tilt it outward.

When the foot is off the ground, inversion occurs as part of a combined movement that turns the sole inward and points the forefoot downward and inward. This combination is also described as supination. Conversely, eversion paired with movement of the forefoot upward and outward is called pronation. These same terms are used in the forearm to describe the direction the palm faces, so consider the context as well.

When you walk or run, your feet move between these two directions to adapt to the ground. Just after the foot touches the ground, it everts slightly to absorb impact. As you push off, it shifts toward providing firm support. Inversion and eversion are therefore not bad movements, but normal ways for the body to adapt to the ground.

When walking on a sloping road or an uneven mountain trail, you may feel that one foot keeps tilting inward or outward. This is a sign that your ankle is working hard to maintain balance.

When you roll your ankle

The most common movement when an ankle is sprained is inversion, in which the foot suddenly rolls forcefully inward. This places a strong pull on the ligaments on the outside of the ankle (lateral collateral ligament of the knee). Injuries in the eversion direction, in which the foot rolls outward, are relatively uncommon and place stress on the structures on the inside of the ankle. For more details about a sprained ankle, see Ankle sprain.

• Ankle circles — Sit with your foot slightly off the floor and draw large circles with your ankle. This exercise gently uses both inversion and eversion. Slowly make 10 circles in each direction.
• Evertor muscle exercise — Loop a resistance band around the outside of your foot and slowly turn the sole outward against the resistance. The muscles on the outside of the lower leg help protect the ankle, so if you have sprained it before, try this slowly.
• Standing on one leg — Stand on one leg for 20–30 seconds and maintain your balance. This engages both the muscles around the ankle and your sense of balance. Once you are comfortable, try closing your eyes or standing on a soft mat.
• Check your shoes — If the sole is heavily worn on just one side, it may be a clue that your foot tends to tilt to one side when you walk. However, treat the wear pattern only as one piece of information when considering your walking pattern.

• Your ankle frequently rolls inward, with a recurring feeling of instability
• Swelling and pain do not decrease even several days after a sprain
• You have difficulty bearing weight, or pressing on the bony areas on the inside or outside of the ankle causes severe pain

In these cases, it is a good idea to have your condition assessed.