Ankle sprains are considered the most common foot injury. An ankle sprain is damage to one or more ligaments surrounding the ankle, of which there are two groups: the thick inside deltoid ligament and the weaker lateral ligaments that receive more stress. Consequently, inversion lateral ligament sprains (the ankle "rolls out") are nine times more likely than eversion deltoid ligament sprains. Common causes of ankle sprains include excessive inversion, eversion, blunt trauma and abnormally weak ligaments.
Inversion
Ankle sprains are most commonly caused by excessive inversion of the foot (internal rotation), which forces the ankle to "roll out," putting tremendous tensile force on the weaker anterior talofibula and calcaneofibula ligaments of the lateral ankle. All ankle ligaments are meant to limit side-to-side movement and provide stability, but many situations increase the risk of inversion sprains, such as playing athletics (basketball, gymnastics, soccer and tennis being the worst), wearing unstable footwear (women's high heels, platform shoes and flip-flops being the worst), walking on uneven ground or around any form of construction, and simply being clumsy. In addition, people who have high arches and walk on the outsides of their feet (called supination) are more susceptible to inversion sprains, although wearing ankle-high athletic shoes and taping ankles can provide valuable support and reduce the frequency of sprains.
Eversion
A much less common type of ankle sprain occurs when the foot experiences excessive eversion (external rotation), which forces the ankle to "roll in," collapse and put tensile force on the deltoid ligament. The degree of ligament damage is usually less with eversion sprains. Again, sports such as basketball, volleyball, football and gymnastics all increase the likelihood of eversion injuries, although weightlifting and track and field activities pose the biggest threat. In addition, people who have flat arches and walk on the insides of their feet (called pronation) are more susceptible to eversion ankle sprains.
Blunt Trauma
The ligaments of either side of the ankle can be injured with blunt trauma, such as what might occur in a motor vehicle accident, a sporting event or a household mishap. Blunt trauma rarely severs ligaments, but it can frequently cause inflammation and tearing as well as joint dysfunction.
Abnormally Weak Ligaments
Ankle sprains sometimes occur because of inherent weak ligaments. A common cause is a poorly healed previous ankle injury. Ehlers-Danlos and Marfan syndromes are examples of congenital diseases that weaken ligaments and connective tissue. In addition, pregnancy (due to the release of the hormone relaxin) can cause hypermobile joints and increase the risks of both inversion and eversion ankle sprains.
References
- "The Foot and Ankle in Sport"; Donald E. Baxter; 1995
- "Biomechanics of the Foot and Ankle"; Robert Donatelli; 1995
- "Gait Analysis: Normal and Pathological Function"; Jacquelin Perry; 1992
