The syndesmosis is the thick band of tissue connecting the two leg bones (tibia & fibula) together just above the ankle. The syndesmosis is very important for ankle stability, and tends to be damaged in more severe ankle fractures.
Symptoms
The pain of a syndesmosis sprain is felt higher up than an ordinary sprained ankle. The signs and symptoms include:
- Pain above the ankle, on the outside, between the two leg bones
- Pain when pushing off, going up stairs or turning
- Swelling above the ankle rather than around it
- Trouble putting weight through the leg, often more than with a normal sprain
- A feeling that the ankle is unstable
Causes
The syndesmosis is damaged when the foot twists outwards while the ankle is bent up. This forces the two leg bones apart. It usually happens in sport, and the football codes, rugby, basketball, skiing and snowboarding are the common settings. It can also follow a heavy fall or tackle.
The same force can break the ankle, so this injury often occurs alongside an ankle fracture.
Risk Factors
The risk is higher in contact and cutting sports. It is also higher in skiing and snowboarding, where the boot holds the ankle while the body twists above it. Other things that raise the risk are:
- A previous ankle injury
- Playing on uneven or slippery ground
Investigations
Your doctor will examine the ankle and press along the leg above it. Two tests are commonly used:
- The squeeze test, which presses the two leg bones together higher up the calf
- The external rotation test, which turns the foot outwards
Both bring on the pain when the syndesmosis is injured.
X-rays are taken to look for a fracture and to see whether the two leg bones have moved apart. These are sometimes taken while you stand, because a small gap may only show under load. CT and MRI are used when the picture is unclear, or when surgery is being planned.
Complications
A syndesmosis sprain takes much longer to recover than an ordinary ankle sprain. This surprises most people, and it is the main reason the injury is returned to sport too early. Problems that can follow include:
- Ongoing pain and stiffness above the ankle
- Arthritis in the ankle, if the two leg bones heal apart
- An ankle that stays unstable
- Bone forming in the tissue between the two leg bones, which can limit movement
- A slower return to sport than expected, or a return at a lower level
Treatment
Treatment depends on whether the two leg bones have moved apart. Where they are still in place, the ankle is rested in a boot or cast. There is usually a period of not putting weight through the leg, followed by physiotherapy. Recovery takes much longer than for a simple ankle sprain.
Where the bones have separated, surgery is needed to hold them together while the ligaments heal. This is done either with a screw passed across the two bones, or with a strong flexible device known as a suture button. A screw is sometimes removed a few months later, once healing is complete, while a suture button is usually left in place. Physiotherapy afterwards builds up strength and balance before return to sport.
Prevention
This injury is hard to prevent, but the risk of ankle injuries in general can be lowered by:
- Balance and strength training for the ankle
- Ski and snowboard boots and bindings that fit and release correctly
- Finishing rehabilitation after any ankle injury before returning to sport
- Taking care on uneven and slippery ground
F.A.Q. | Frequently Asked Questions
How is a high ankle sprain different from a normal sprain?
A normal sprain tears the ligaments on the outside of the ankle. A high ankle or syndesmosis sprain tears the ligaments that hold the two shin bones together just above the ankle. It hurts higher up, hurts when the foot is turned outwards, and takes about twice as long to heal.
How long will I be out of sport?
Usually 6 to 8 weeks for a sprain treated in a boot, and 3 to 4 months if surgery is needed. This is longer than a normal ankle sprain even though the ankle may look less swollen.
Do I need surgery?
Only if the two shin bones have separated or the ankle is unstable on an X-ray or MRI. Most syndesmosis sprains heal in a boot with the weight kept off at first.
What is a tightrope or syndesmosis screw?
They are two ways of holding the shin bones together while the ligaments heal. A screw is rigid and is often removed later. A tightrope is a strong cord with buttons that allows a little movement and usually stays in.