An ankle sprain refers to the tearing of the ligaments of the ankle and account for approximately 40% of all athletic injuries. 85% of ankle sprains occur on the outside (lateral side) of the ankle and are known as an inversion sprain. This is the type of injury that most runners experience when they sprain their ankles. Medial ankle sprains (along the inside of the ankle) occur less frequently and are usually caused by fractures or other traumatic events.
So, why is an inversion sprain so common? You can put it down to our lopsided anatomy! The bone on the lower outside of the ankle (the lateral malleolus - distal fibula) extends further down than the bone on the inside of the ankle (medial malleolus – fibula). This difference gives the inside of the ankle (medial side) more stability than the outside of the ankle (lateral side).
At a symptomatic level, most ankle sprains appear to resolve completely without rehabilitation. In reality, ankle sprains that have not been rehabilitated correctly are usually susceptible to further injury.
Anatomy of an Ankle Sprain
The outside (lateral side) of the ankle achieves its stability from a three-ligament complex. These three ligaments are the:
In an inversion sprain, the Anterior Talofibular ligament (ATFL) is the most commonly injured. Ligaments in the ankle are named according to the bones to which they connect. In this case, the Anterior Talofibular ligament connects to the talus bone of the ankle as well as to a long bone of the lower leg - the fibula. The function of the ATFL is to prevent forward (anterior) displacement of the ankle (the talus).
In a severe ankle sprain another ligament called the calcaneofibular ligament (CFL) may also be damaged. This ligament connects your heel bone (calcaneous) with the fibula. This is a stronger ligament than the ATFL, and is not damaged as easily.
Both the ATFL and the CFL are usually damaged in motions where the foot is both pointed down (plantar flexed) and rolled out (inverted). Considerable instability in the ankle can occur when both these ligaments are injured.
The posterior talofibular ligament (PTFL) is not injured very often, except when there is a complete dislocation of the ankle (talus). The PTFL is the strongest ligament in the lateral complex.
Another sprain injury that is becoming more prevalent is called a “High Ankle Sprain” (syndesmotic ligament complex). In this injury, the ligament and connective tissue between your shin bones (tibia and fibula) are torn. This is a serious injury that may require surgery to resolve.
Not Just Ligaments
An ankle sprain may also result in damage to other structures. You may also experience damage to connective tissue, tendons, muscles further up the ankle, and even to the bones (possible fractures). This is why, with a severe ankle sprain, it is important to see a medical professional who can determine exactly which structures have been injured, and then provide treatment recommendations.
In Part Two of Ankle Sprains or Inversion Sprains we will cover: Determining the Severity of an Ankle Sprain and Initial Treatment for Ankle Sprains.
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