A syndesmosis or high ankle sprain is a more serious type of ankle sprain. It accounts for up to 15% of all acute ankle injuries and is particularly common in contact football codes. So what is a high ankle sprain and how does it happen?
The syndesmosis or distal tibiofibular joint is the joint formed between the two bones in the lower leg, the tibia and fibula. These bones have several strong ligaments joining them together just above the ankle joint. A syndesmosis sprain occurs when these ligaments are injured, often termed a “high ankle sprain” as the injury occurs just above the ankle joint.
Why is this a more significant problems than a regular ankle sprain? Because the ankle bone (the “talus”) will be driven up between the tibia and fibula towards the knee with every step. Clearly this will hurt! It also makes walking or running after a high ankle sprain far more difficult than after a regular lateral ligament sprain (see our blog for more information about lateral ankle sprains).
Injury to the syndesmosis occurs most commonly when the foot is weight bearing in a dorsiflexed position (as in a semi-squat position. This is the opposite of a plantar flexed position where the toes are pointed). The ankle bone (talus) is wider at the front than the back, like a wedge, so in the dorsifexed / squat position it tends to force the tibia and fibula apart. When an external rotation force is added, the syndesmosis ligaments can rupture. This dorsiflexion / external rotation combination occurs in the real world in football tackles, when the player is in a semi-squat position and gets tackled from one side, twisting the ankle whilst all of his/her weight is on it.
Like other ankle sprains, the high ankle sprain is very painful. There tends to be less swelling than other sprains, and any swelling present tends to sit on the front of the ankle joint (lateral sprains tend to have a more swelling and bruising located on the outside of ankle). It is much harder to walk or run when compared to other sprains and crutches are often preferred.
There is a high incidence of other injuries occurring when you damage the syndesmosis. This includes painful bone bruises (see our blog here), damage to the cartilage in the ankle joint, microfractures and injury to other ligaments.
I can’t emphasise this enough – get in early for professional diagnosis and treatment after ANY ankle sprain, but especially this one. You can get some certainty about what you have done and get started on an appropriate treatment and rehab program faster so your short term and long term result is better. We can evaluate how extensive the damage is and how associated injuries will modify your treatment.
Delaying professional assessment causes potentially big problems:
1. Diagnosis is harder, less accurate and even MRI scans will underestimate the severity of your injury if performed late (Randell et al 2019). Accurate diagnosis, particularly for injury severity, is crucial for getting your treatment correct.
2. Delayed diagnosis and poor management can lead to :
A. Scar tissue formation that may require surgical removal at a later date;
B. Chronic instability (you keep spraining your ankle or it keeps giving way);
C. Osteoarthritis (permanent painful joint damage);
D. Heterotopic ossification (which is bone formation in your soft tissues in an attempt to heal, causing pain that may need later surgical removal).
Diagnosis focuses on determining whether the syndesmosis is stable or unstable as this decision determines treatment. This requires clinical tests and imaging. Please understand that ALL of the clinical tests and imaging are far more accurate if performed in the first 5-10days following injury (Randell et al 2019), so doing nothing and “just hoping it’ll get better” actually harms your chances of a good outcome.
In the case of an unstable joint, surgery is universally regarded as the treatment of choice.
For stable injuries, conservative care produces excellent results. This involves immobilisation in a moon boot and crutches for 2-4weeks. A specific ankle brace for the syndesmosis, which differs from those used for lateral or medial ligament sprains, is then used for a further 6 weeks and during return to sport. Rehab and the brace are also required after surgery. Rehab works! There is excellent science to prove this. Rehab needs to be professionally prescribed to prevent further ankle damage or causing continued joint inflammation. It needs to be progressed up to the sport-specific level you intend to return to. Note that it takes longer to return to sport with a high ankle sprain when compared to the more common lateral ligament injury. Trying to rush back causes further problems (for example formation of a cyst between the tibia and fibula which prevents healing) so a little more patience is required with this type of injury.
“Hoping it’ll get better” is never the best treatment for any ankle sprain, especially the more serious ankle injuries such as a syndesmosis sprain, so seek the professional care of your Physiotherapist straight away. I can refer you for an MRI scan and perform all of the relevant diagnostic tests and get you started on the appropriate course of treatment immediately. Not doing rehab is associated with a high recurrence rate and chronic ankle instability.
Randell et al (2019): MRI for high ankle sprains with an unstable syndesmosis: posterior malleolus bone oedema is common and time to scan matters. Knee Surgery, Sports Traumatology, Arthroscopy 27:2890- 2897.