The syndesmosis refers to the “high ankle” – the unification of the tibia and fibula (two long bones of the shin. These bones are stabilised strongly by a number of important structures including:
- Interosseous membrane
- Deltoid ligament
Injuries to the syndesmosis are often mistaken for “garden variety” lateral ankle sprains. The most common mechanism of injury involves external rotation of the foot relative to the shin. Pain is often quite diffuse and due to movement of swelling will often spread further down the foot and ankle in the hours after injury.
Confirmation of syndesmotic injury usually involves:
- Weightbearing X-ray (to observe for separation of the tibia and fibula)
- Squeeze test
- External rotation test
- Specific palpation of the syndesmotic ligaments
- MRI (to help clarify the degree of damage to ligaments)
It is extremely important to diagnose syndesmosis sprains to ensure appropriate treatment. Healing times are often slower than an inversion sprain and in most cases require a period of immobilisation in a CAM boot. Surgery may be required for complete ruptures that lead to significant instability across the joint. In either case a thorough period of strengthening and proprioceptive retraining will be needed in order to restore normal ankle function and return to sporting activities.
In my experience it is not uncommon for people to present to the clinic with an “ankle that just isn’t improving” several weeks after the initial injury, having continued to fully weight bear on a syndesmosis sprain.
Andrew Robertson, Physiotherapist, Evoker.