Syndesmotic Injuries – High Ankle Sprains

A high ankle sprain is a partial or complete tear of the ligaments above the ankle joint. A ligament is a strong fibrous band which connects bone to bone. Ligaments provide stability to joints and unlike tendons, they do not stretch. A sprain is an injury to a ligament, which could be a stretch, partial or full tear of the fibrous tissue band. The ligaments above the ankle joint are called the syndesmotic ligaments and commonly referred to as the syndesmosis. There are three main ligaments which connect the tibia, also known as the shin bone, to the fibula, the thin bone which sits adjacent to the tibia at the outside of the leg. A connective tissue sheet, called the interosseous ligament, connects the fibula to the tibia and extends from the knee to the ankle.

A syndesmotic injury is caused when the foot rotates outward and is forced upward. This type of motion can occur in sports such as hockey, football, soccer and skiing. Syndesmotic injuries can occur in isolation or with an ankle fracture. When they occur in isolation, they may present with very little swelling or bruising, which makes diagnosis difficult. Mild syndesmotic injuries may have some swelling and bruising on the outside of the ankle and more severe injuries are associated with ankle instability.

Diagnosis is made by physical exam and radiographic evaluation. Squeezing the calf and externally rotating the leg will elicit pain and the front of the ankle is very tender to direct palpation. An X-ray will rule out fractures and other conditions, but will also help evaluate the severity of the injury. A stress X-ray is taken with the foot angled outward and a gap between the tibia and the fibula is indicative of a more severe syndesmotic injury. An MRI or a CT Scan may aid in diagnosis, but are typically more beneficial when evaluating more severe syndesmotic injuries.

When only one ligament of the group of syndesmotic ligaments is stretched or partially torn, the injury is considered mild and the ankle is usually stable. Treatment is similar to treatments for common ankle sprains and involve anti-inflammatory medications, ice, compression and immobilization. Early weight bearing is generally recommended for ankle sprains, but if a syndesmotic injury is suspected, crutches will be needed before progressing to rehabilitation. Recovery time will be between 1-2 months.

If two or three of the ligaments are torn, the ankle becomes unstable. If stress X-rays reveal gapping between the tibia and fibula, surgery involving placement of a screw across the leg bones may be necessary. A key component of ankle instability is the integrity of the deltoid ligaments. The deltoid ligaments extend from the inside of the ankle at the base of the tibia (medial malleolus) to the bones in the foot. When the deltoid ligaments are torn, ankle stability is severely compromised. Studies have shown that the most important determining factor indicating the need for surgery in syndesmotic injuries is injury to the deltoid ligaments. When the ankle is unstable and surgery is required, recovery time can take up to 6 months. The first few weeks require non-weight bearing and ankle immobilization, but after 2-4 weeks active mobilization and physical therapy can be initiated. The amount of activity can increase after 6-8 weeks, with full impact activity beginning at around 3 months.