Your lower leg bones (tibia and fibula) are held together at the ankle by a group of soft tissues and ligaments called the “syndesmosis”. This connection prevents excessive spreading of these bones during normal activity, but injuries can cause these ligaments to be stretched or torn. This problem is called a “syndesmotic ankle sprain” or “high ankle sprain”. High ankle sprains often occur during contact sports (like football, hockey, and soccer) when your foot is planted while the rest of your body shifts forward and turns inward. High ankle sprains are much less common than other types of ankle sprains.
The pain of a high ankle sprain starts just above your ankle and runs up your shin. Interestingly, the “length” of pain correlates very closely to your severity of injury. Standing and walking is usually uncomfortable and sometimes unbearable. Bringing your toes toward your shin or rotating your foot outward will likely increase your pain. Significant bruising or swelling is possible. Be sure to tell your doctor if you notice numbness, tingling, or coldness in your foot.
Ankles that have suffered a complete separation usually require surgery, since they will have lost the ability to push off, propel, and cut. Most other stable sprains will respond to conservative care, like the type provided in this office. It is important to recognize that high ankle sprains heal more slowly than other types of ankle sprains. The average recovery time for a syndesmotic sprain is between two and seven weeks but some injuries may require up to four months away from your sport. You may need to wear a boot or avoid weight bearing for a period of time. Ice may help to limit swelling initially, and the home exercises described below are an important part of your recovery.
“Syndesmotic ankle sprain” or “high ankle sprain” follows damage to the ligaments and tissues that hold the tibia and fibula together at the ankle mortise joint. Syndesmotic sprains are much less common than their lateral counterparts (representing less than 10% of all ankle sprains) but are more difficult to assess and manage with significantly longer recovery times. (1-3)
The ankle mortise joint is comprised of the (slightly concave) tibia and the (slightly convex) fibula, which rest on the talus. (4,5) These three bones are held together by three ligaments: the anterior tibiofibular ligament (AITFL), the posterior tibiofibular ligament (PITFL), and the interosseous membrane. The triangular shaped AITFL begins with a broad origin on the anterolateral tibia and runs obliquely to a point on the anterior aspect of the lateral malleolus. (5-7) The more horizontally oriented PITFL is comprised of a superficial band and a deeper component (inferior transverse ligament) that together connect the posterior aspects of the tibia and fibula. (5,7) Finally, the interosseous membrane connects the medial aspects of the tibia and fibula along their entire length. (4) The distal termination of the interosseous membrane consists of a fibrotic thickening called the interosseous ligament that further stabilizes the joint. (6,9)
The primary function of the syndesmotic ligaments is to prevent excessive widening of the ankle mortise by holding the fibula tight to the tibia. (10) During normal ankle dorsiflexion, the wider anterior aspect of the talus wedges and spreads the tibia and fibula by 1-2 millimeters. (10,11) Additionally, ground reactive forces cause approximately 5 degrees of external rotation of the talus, which forces the fibula laterally. (10) The distal fibers of the interosseous membrane act in a spring-like fashion to accommodate this separation during dynamic loading.
Disruption of the syndesmosis occurs from forces that cause excessive mortise widening- particularly external rotation (pushes the fibula laterally) and hyperdorsiflexion (wedge effect). (11,13-17) Isolated external rotation injuries produce a predictable pattern of damage, commensurate to the force involved. First, the deltoid ligament is ruptured (or the medial malleolus is avulsed), followed by progressive tearing of the AITFL, the PITFL, and finally, the interosseous membrane. (18) Particularly forceful injuries may terminate in a spiral fracture to the proximal fibula (Maisonneuve fracture) (18)