An ankle sprain occurs when the tough, fibrous bands of connective tissue called ligaments are stretched or torn. While the term “sprained ankle” is used generally, there are distinct types of injuries defined by which ligaments are damaged. The two primary categories are the low ankle sprain, which is the most common, and the high ankle sprain, which involves a different set of structures. Understanding the location and function of the affected ligaments is important for determining the injury’s severity and necessary treatment.
Understanding the Injury Locations
The common low ankle sprain involves ligaments on the outside (lateral aspect) of the ankle joint. This injury typically affects the lateral ligament complex, most often the anterior talofibular ligament (ATFL). Low ankle sprains usually happen when the foot forcefully rolls inward, a mechanism known as inversion, which overstretches these tissues.
A high ankle sprain, also known as a syndesmotic injury, involves the ligaments connecting the two lower leg bones: the tibia and the fibula. These ligaments form the syndesmosis, located just above the ankle joint. The primary structures damaged are the anterior inferior tibiofibular ligament (AITFL) and the posterior inferior tibiofibular ligament (PITFL). These injuries are typically caused by a high-energy mechanism, such as forceful external rotation and upward flexing of the planted foot.
Differences in Stability and Severity
The high ankle sprain is generally considered more severe because it compromises the fundamental stability of the entire ankle complex. The syndesmotic ligaments tightly bind the tibia and fibula together, forming a strong socket called the ankle mortise. This mortise holds the talus bone of the foot securely in place and is under considerable stress with every step.
When the syndesmosis is damaged, the tibia and fibula can spread apart, destabilizing the entire joint. This disruption to the ankle mortise results in greater pain when bearing weight and higher functional instability than a low ankle sprain. In contrast, a low ankle sprain affects ligaments that primarily limit excessive movement of the foot, such as inward rolling. While the ankle may feel unstable, the structural integrity of the main weight-bearing joint is typically preserved.
Contrasting Treatment and Recovery Timelines
The difference in severity directly influences the approach to treatment and the expected recovery time. Mild to moderate low ankle sprains often respond well to conservative management, including the RICE protocol (Rest, Ice, Compression, Elevation) and early mobilization. A Grade I low ankle sprain may heal within one to three weeks, while a severe Grade III sprain can take up to twelve weeks for full recovery.
High ankle sprains require more cautious and prolonged immobilization due to the syndesmosis’s role. Even a mild high ankle sprain can take six to eight weeks to recover, and severe cases may take three to four months or longer. Because weight-bearing places high stress on the injured syndesmotic ligaments, patients are often kept non-weight-bearing for a period to allow proper healing. If the injury causes significant widening of the ankle mortise, surgical intervention may be necessary to stabilize the bones and prevent chronic instability.