The human ankle consists of three joints: the talocrural joint (a hinge joint formed by the distal fibula and tibula and the talus), the inferior tibiofibular joint (a strong joint between the lower tibia and fibula), and the subtalar joint (the main ankle joint comprising the talus and the calcaneus). These joints are connected by two main ligaments: the weaker outside lateral collateral ligament group, and the stronger inside medial collateral ligament, all of which provide stability by limiting side-to-side movement. An ankle sprain is an injury to one or more ligaments surrounding the ankle. Ligament injury can be mild (merely stretched), moderate (partially torn), or severe (completely torn). Common causes of ankle sprains include athletic injury, non-athletic injury, weak ankles from previous injury and weak ankles from inborn conditions.
Athletic Injuries
Ankle sprains are most commonly caused by trauma suffered while participating in athletics, especially among males. Sports such as soccer, basketball and most racket sports create conditions that increase the risk of ankle sprains because the ankle is vulnerable to turning over on itself laterally. In soccer, for example, a sudden sideways or twisting movement of the foot can injure the lateral ligaments. In basketball, a player coming down with a rebound can land on another's foot unevenly, which inverts the foot and causes ligament sprain. In racket sports, aggressive lateral sliding movements put tremendous strain on all ankle ligaments. Wearing ankle-high athletic shoes and taping the ankles both reduce the number of ankle sprains within athletics, but ankle sprains are still the most common foot injuries and among the most common orthopaedic injuries.
Non-athletic Injuries
Ankle sprains often occur by simply walking or running on uneven surfaces, or stepping into a hole, or misjudging a step. This is further aggravated by wearing inappropriate footwear, usually high heels with narrow, unstable bases. The ankle joints are at greater risk of sprains because the foot tends to laterally slip off the narrow, unstable shoes. When an ankle rolls over to the outside, it's called an inversion sprain. Inversion sprains account for 90 percent of ankle sprains. Eversion sprains, which occur when the ankle collapses in on itself (forcing the foot laterally), account for the other 10 percent.
Weak Ankles From Previous Injury
Previous ankle injuries that do not heal properly can also predispose the ankle to frequent future sprains. Poor rehabilitation of a previous sprain is a common culprit, but nerve damage (altered proprioception or motor control), reduced blood circulation or weak tendons also are contributing factors. The ligaments most often injured with inversion sprains are the weaker lateral collateral group (the anterior talofibula ligament commonly in lesser injuries, but also the calcaneofibula ligament in more severe injuries).
Weak Ankles From Inborn Conditions
Ankle sprains sometimes occur because of inherently weak ligaments. Marfan and Ehlers-Danlos syndromes are examples of congenital diseases that affect and weaken ligaments and connective tissue. In addition, people with higher arches who supinate while walking (walk on the outer foot edges) are at higher risk of inversion sprains compared to those who have flat arches and pronate.
References
- Ankle Sprain Facts
- "Essentials of Physical Medicine and Rehabilitation"; Brian J. Krabak, M.D., M.B.A. et al; 2008
- "Surgery of the Foot and Ankle"; Michael J. Coughlin, M.D. et al; 2007
