An ankle sprain is the partial or complete tear of the ligaments in the ankle. The classic ankle sprain is caused when the foot rolls in and the ankle rolls out, resulting in tearing of one or more of the ligaments on the outside of the ankle. A high ankle sprain is an injury to a group of ligaments above the ankle joint. The ligament group above the ankle joint is known as the syndesmosis or the syndesmotic ligaments. These ligaments join the tibia (leg bone) and the fibula together and act to hold the ankle joint in place and provide stability and support. Injury to this groups of ligaments can cause severe ankle instability. In the image to the left, the interosseus ligament is shown. This ligament connects the tibia and the fibula and extends from the knee to the ankle.
The injury is caused when the leg and foot twist out and is more commonly seen in sports such as hockey, football and soccer. A syndesmotic injury can occur with a low ankle sprain or an ankle fracture. When the injury occurs in isolation it can be difficult to diagnosis because swelling and bruising may be minimal. Squeezing the calf or lower leg generally results in pain as does externally rotating the leg. When one ligament of the group is torn, the ankle may still be stable and recovery time will be between 1-2 months. If two or three of the ligaments are torn, the ankle becomes unstable, gapping is seen between the tibia and fibular on X-ray and surgery involving placement of a screw across the leg bones is necessary. Recovery time can take up to 6 months after surgery.