The Ankle Joint
The ankle joint is made up of three bones, the tibia, the fibula, and the talus. These bony elements are supported by multiple ligaments that can be divided into three groups: the lateral ligament complex, the deltoid medial ligament, and syndesmotic ligaments which hold together the tibia and fibula where the joint forms. These ligaments attach bone structures together and provide stability to the joint.
The ankle is described as a hinged joint which is responsible for upward motion (dorsiflexion), downward motion (plantar flexion), inward rotation (inversion), and outward rotation (eversion) of the foot. The ankle joint is crucial for ambulation because it allows the foot to adapt to the surface it is walking on and capable of sustaining loads as much as three times the body's weight.
Low Ankle sprain (common ankle sprain)
When physicians refer to ankle sprains they are describing injuries to the ligaments that attach the bones of the ankle joint. An ankle sprain can occur to either the inside (medial) or the outside (lateral) ligaments of the ankle. These structures may stretch and tear when the joint is forced into an unnatural position. The most common mechanism of injury to the ankle joint is inversion of the foot which mainly affects the three ligament that form the lateral ligament complex, these are the anterior talofibular ligament (ATFL), the posterior talofibular ligament, and the calcaneal fibular ligament. With a common ankle sprain where the foot is forcefully inverted, the ligament that suffers the most damage is the ATFL. Eighty percent of all low ankle sprains are due to forceful inversion, the remainder are due to forceful eversion which affects the deltoid medial ligament. The severity of the sprain corresponds to the degree of involvement of these three ligaments. A grade I ankle sprain involves the ATFL alone, a grade II sprain involves two ligaments, and a grade III involves all three ligaments.
Diagnosis of ankle sprains relies mainly on patient history, physical exam findings, and imaging (i.e. X-rays, CT, MRI) to rule out fractures, other sites of injury, and to assess severity. People who suffer a low ankle sprain injury will frequently have pain with weight bearing, swelling, stiffness, and even bruising in more severe sprains. Also, there is usually an area of tenderness which corresponds to the site of injury; on physical exam, joint laxity may be observed on the corresponding ligament.
High ankle sprain (syndesmotic ankle injury)
In contrast to low ankle sprains, a high ankle sprain happens when there is shearing damage done to the syndesmotic ligaments, these are the ligaments that hold together the tibia and fibula above the talus. When bearing weight on the leg, the tibia and fibula experience strong forces that spread them apart. The syndesmotic ligaments, or syndesmosis, serve as shock absorbing cables that prevent these two bones from spreading too far apart. High ankle sprains commonly occur when the foot and ankle rotate together such as sudden twisting, turning, or cutting motion seen in high-impact sports like football, basketball, and soccer.
Diagnosis of a high ankle sprain is also based on patient history, physicial exam, and imaging to rule out fractures or compartment syndrome. High ankle sprains may be frustrating for patients because clinically they do not "look that bad", meaning that they do not cause as much swelling or bruising as seen with low ankle sprains. Because of this, patients can become unaware of the severity of their injury which can eventually affect the recovery and healing process. Still, people who suffer high ankle sprains may have severe pain that radiates up the leg with each step and can become worst when doing movements that are similar to how the injury occurred. On physical exam, there are provocative test which may illicit pain such as the squeeze test (compressing the tibia and fibula at midcalf) and external rotation stress test (external rotation/dorsiflexion of the foot with knee and hip flexed at 90 degrees).
Treatment and Recovery
Whether it is a low ankle sprain or a high ankle sprain, conservative treament for both types of injuries include: RICE protocol (rest, ice, compression, elevation), NSAIDs for pain and anti-inflammatory relief, and physical therapy to regain motion and functionality. Further treatment options will greatly depend on the severity of the injury. In the case of low ankle sprains, ankle braces may help provide additional stability to the joint and prevent future sprains, especially in those patients who have history of recurrent sprains. On the other hand, severe high ankle sprains may require a non-weight bearing walker boot or cast for two to three weeks to delay weight bearing until healing ensues. Unless there is evidence of a complete tear or fractures present, surgery is not considered.
Recovery from any type of ankle sprain will also depend on severity. A grade I low ankle sprain can fully recover in days to a couple of weeks, while a grade III sprain can take up to twelve weeks. In the case of high ankle sprains, they generally require a longer recovery and rehabilitation period in comparison to low ankle sprains, this can take anywhere from six weeks to three months and in some cases even more. The key for a successful recovery is to allow healing to occur without applying excessive stress on the ankle, and with proper therapy and exercise regain strength and functionality back to normal.
