The ankle region consists of four bones: the distal portions of tibia and fibula, the calcaneus and the talus. The interaction of these bones creates three separate joints, which are connected by two main ligaments: the lateral collateral ligament group (on the outside) and the medial collateral ligament (on the inside). The ankle ligaments provide stability by limiting side-to-side movement. An ankle sprain is an injury to one or more of the ligament bands surrounding the ankle joints. The severity of an ankle sprain depends on whether the ligament is merely stretched, slightly torn, or completely torn, as well as on the number of ligaments involved. Common causes of ankle sprains include sports trauma, wearing inappropriate footwear, common accidents, previous unhealed ankle injury, and congenital conditions which weaken ligaments.
Sports Trauma
The most common cause of ankle sprains is trauma suffered while playing sports, especially among men and boys. Basketball, soccer, and tennis are common sports, which all create conditions that greatly contribute to ankle sprains because the ankle is vulnerable to "rolling over" itself. In basketball, it typically occurs when one player jumps up and comes down on another player's foot unevenly. In soccer, it might occur with a sudden turn, or a lateral blow from a tackle. In tennis, extreme lateral stop-and-go movements put tremendous strain on the lateral ligaments. When an ankle rolls over laterally on itself, it is called an inversion sprain, which accounts for about 90 percent of ankle sprains. An eversion sprain is when the ankle "rolls in" on itself (forcing the foot laterally) and accounts for the other 10 percent.
Inappropriate Footwear
The next most common cause of ankle sprains can be attributed to wearing inappropriate shoes that have high heals with narrow bases, which creates instability. Women's high heels are obvious examples, but fashion trends also put men at risk. Again, the ankle joints are mainly in jeopardy of inversion sprains because the foot tends to topple off the unstable shoe laterally. The ligaments most often injured with inversion sprains are the lateral collateral group, specifically the anterior talofibular ligament, although if the ankle sprain is severe, the calcaneofibular ligament can also be involved.
Common Accidents
Ankle sprains can sometimes be caused by simply walking or running on an uneven surface, or not seeing a curb or a step, despite wearing appropriate shoes and in the absence of trauma. People with high arches and who supinate when they walk (put more weight on the outside of the feet) are at higher risk of inversion sprains than those who are pronators and have collapsed arches. Due to the ease of injury, ankle sprains are among the most common orthopedic injuries, and specifically the most common foot injury.
Previous Unhealed Ankle Injury
Previous ankle or foot injuries can also weaken the ankle and lead to sprains more readily. Usually, poor rehabilitation of a previous sprain, reduced proprioception (positional sensing), nerve damage, reduced blood circulation, or weak tendons and muscles are contributing factors.
Congenital Conditions
Sometimes, ankle sprains occur because a person is born with weak ligaments. Marfan syndrome and Ehlers-Danlos syndrome are diseases that affect and weaken ligaments and connective tissue.
References
- Anatomy of the Ankle
- "The Unstable Ankle"; Meir Nyska D.P.M. et al; 2002
- "The Foot and Ankle in Sport"; Donald E. Baxter; 1995
