Ankle sprains are the most common orthopedic injuries, and most of these result from injury to the lateral ankle ligaments. Lateral ankle sprain is quite common among sportspersons and accounts for about 10 -15% of all sports-related injures. Volleyball, basketball and soccer players are most at risk of acquiring a lateral ankle sprain. However, a person can twist his ankle even while walking normally during routine activities.
The ankle joint is formed between the bones of the lower leg tibia and fibula and those of the hind foot, mainly the anklebone (talus).
A number of ligaments hold these bones in the ankle joint. These ligaments are divided into two main groups. The ligaments located on the outside of the ankle are called lateral ligaments. The ligaments located on the inner side of the ankle are called medial ligaments (deltoid ligaments).
There are three major ligaments located on the outer side of the ankle, which join the fibula (the bone on the outer side of the leg) to the anklebone (talus) and heel bone (calcaneus).
the anterior talo-fibular ligament (joining the fibula to the talus, located in the front)
the calcaneo-fibular ligament (joining the fibula to the calcaneus, located in the middle)
the posterior talo-fibular ligament (joining the fibula to the talus, located at the back)
In a lateral ankle sprain, the ligament located in the front, i.e. the anterior talo-fibular ligament, takes most of the impact, and therefore it is the one most commonly injured.
The ligament in the middle, the calcaneo-fibular ligament, is a strong ligament, but in severe cases, it may also be involved. The posterior talo-fibular ligament, which is located further back, is involved only rarely.
Lateral ankle sprain occurs due to accidental inward rolling (inversion) of the foot. This can happen while walking on an irregular surface, jumping and running (as in sports), walking in ill-fitting or high-heeled shoes, etc. When the foot twists inwards, the ligaments on the outer side of the foot are stretched beyond the normal range and are torn. The ligaments may also be damaged due to a direct impact. The extent of damage depends upon the extent to which the foot is twisted, and can be categorized into:
Grade I sprain: minimum damage, the ligament is overstretched, little pain and swelling, minimal or no functional impairment
Grade II sprain: moderate damage, the ligament is partially torn, moderate pain and swelling, impairment of function, difficult to walk or put pressure on the affected joint
Grade III sprain: severe damage, the ligament ruptures completely, resulting in joint instability, severe pain and swelling, making it impossible to stand or walk on the affected side
Persons who have previously suffered from an ankle sprain are twice as likely to acquire another sprain. Moreover, people born with weak ankles, obese persons or those involved in vigorous sports also have an increased risk of suffering from a lateral ankle sprain.