Unstable ankle fracture
An ankle fracture in which the joint alignment is disrupted - either by displaced bones, ligament injury, or both. Unstable fractures usually require surgery to restore alignment and allow the joint to heal correctly.
📊 Unstable patterns make up approximately 30-40% of ankle fractures. Around 90% of these require surgical fixation. Ankle fracture incidence has doubled over the last 30 years, driven in part by population ageing.
What is an unstable ankle fracture?
In an unstable ankle fracture, the talus no longer sits correctly within the mortise formed by the tibia and fibula. This can happen for two reasons: either the bones are displaced (broken and out of position), or the ligaments holding the joint together are torn. Both situations alter the way load passes through the joint. If left to heal in this position, ankle arthritis is highly likely within a few years.
Common unstable patterns include: bimalleolar fractures (both medial and lateral malleoli broken); trimalleolar fractures (medial, lateral, and posterior malleoli); high fibula fractures with deltoid ligament rupture (Weber C with medial-sided injury); and syndesmotic injuries with widening of the tibiofibular joint. In each case, surgical fixation is needed to restore the precise anatomy of the joint.
Surgery aims to restore the joint to its pre-injury position and hold it there while the bones heal. This usually involves a plate and screws on the fibula, a screw or wire on the medial malleolus if broken, and sometimes a syndesmotic screw or suture button across the lower tibia and fibula. Early surgery (within 24-72 hours, before significant swelling) is preferred where possible.
Common mechanisms
- High-energy twisting injury
- Fall from a height
- Road traffic collision
- Sports injury - particularly rugby, football, skiing
- Lower-energy injuries in older adults, particularly with osteoporosis
Who is at risk? Risk factors are similar to stable fractures but with greater contribution from high-energy mechanisms. Diabetes, smoking, and peripheral vascular disease all increase the risk of complications and worsen outcomes after surgery.
Symptoms
Symptoms typically begin at the time of injury and can vary depending on the severity:
- Severe pain immediately after the injury
- Inability to weight-bear
- Marked deformity of the ankle - sometimes the foot appears to be pointing the wrong way
- Rapid and extensive swelling
- Bruising around the ankle and lower leg
- Sometimes pale or numb foot if blood supply or nerves are compromised
When to seek help: Attend A&E immediately - this is a true emergency. Severe deformity, pale/blue toes, or numbness are red flags suggesting compromised blood supply or nerves, which require urgent reduction.
How is it diagnosed?
Your foot and ankle specialist will take a detailed history and examine the foot. The following investigations may be arranged to confirm the diagnosis:
- Immediate plain X-rays - AP, lateral, and mortise views
- Stress X-rays or weight-bearing X-rays - confirm instability where there is doubt
- CT scan - often used to fully define the fracture pattern, particularly with posterior malleolar or pilon fractures
- MRI - occasionally used to confirm syndesmotic or deltoid ligament injury
A "trimalleolar equivalent" injury exists where the medial side is held by a torn deltoid ligament rather than a fracture - these are just as unstable as a true trimalleolar fracture and require the same management.
Treatment pathway
Treatment depends on the severity of the injury, your age, and your activity demands. Many injuries can be managed without surgery; others require surgical fixation.
Reduction and backslab
If displaced, the ankle is reduced (manually realigned) under sedation in A&E, and held in a plaster backslab. X-rays repeated to confirm position. Reduction reduces pressure on the skin and reduces the risk of complications.
Early surgery (if appropriate)
If swelling is not too severe, surgery within the first 1-3 days gives the best outcomes. Open reduction and internal fixation (ORIF) uses plates and screws to restore the anatomy.
Wait for swelling to settle
If significant swelling is present, surgery may be delayed for 7-14 days to allow swelling to settle. This reduces wound complication rates. The ankle is held in a temporary plaster meanwhile.
Syndesmotic fixation
For high fibula fractures or syndesmotic injuries, a screw or suture button across the lower tibia and fibula is added to hold the syndesmosis together while it heals. Screws are sometimes removed at 3-6 months.
Boot or cast and progressive weight-bearing
Most patients are non-weight-bearing for 6 weeks, then progressively weight-bearing in a boot. Newer evidence supports early weight-bearing in selected cases, with good outcomes.
Recovery
Recovery from an unstable ankle fracture is significantly longer than from a stable one. Most patients are non-weight-bearing for 6 weeks. Walking comfortably typically takes 4-6 months. Stiffness, particularly with the upward bend of the ankle, is common and often improves over 12-18 months. Metalwork is rarely removed unless it causes problems.
- Surgery and initial recovery: 0-2 weeks
- Cast or boot, non-weight-bearing: 0-6 weeks
- Progressive weight-bearing in boot: 6-12 weeks
- Out of boot, into shoes: 12-16 weeks
- Walking comfortably: 4-6 months
- Return to sport: 6-9 months
What results can I expect?
Outcomes after successful surgery are generally good. Around 70-80% of patients return to their pre-injury level of function. The main long-term risk is post-traumatic ankle arthritis, which develops in around 20-40% of patients depending on the severity of the injury and how well the joint was reconstructed. Smoking, diabetes, and poor reduction quality all increase this risk.
In numbers
When can I…?
Typical activity timelines for this condition. These are approximate and vary considerably between patients. Always follow the specific guidance given by your surgeon and physiotherapist.
| Activity | Typical timeline | Notes |
|---|---|---|
| Non-weight-bearing | First 6 weeks | After surgery, most patients are non-weight-bearing for 6 weeks. Crutches and elevation are essential.[1] |
| Drive | 10-12 weeks after surgery | When out of cast/boot, able to weight-bear comfortably, and can perform an emergency stop. Inform your insurer.[3] |
| Sedentary work | 2-4 weeks | Office work with the foot up is possible, but transport and access can be limiting in the first few weeks. |
| Standing/manual work | 3-4 months | Manual jobs usually need 3-4 months off after fixation of an unstable ankle fracture.[1] |
| Walk in normal shoes | 10-14 weeks | Out of the boot once X-rays confirm healing and progressive weight-bearing has been tolerated.[1] |
| Return to sport | 6-12 months | Full return to running and cutting sport takes many months. Swelling and stiffness can persist for a year.[1] |
Is this normal?
Common concerns from patients with this condition or recovering from treatment, and whether they are expected or worth mentioning to your team.
Related injuries & conditions
Your questions, answered
Plain-English answers to the things people most often ask, grounded in published guidance. Tap a question to open it.
About thisWhat makes a fracture “unstable”?
An unstable ankle fracture is one where the joint alignment is disrupted, by displaced bones, ligament injury, or both. The ankle is a weight-bearing joint, so alignment matters.
These usually need the bones putting back into position.
Your choiceWhy is surgery usually advised?
Surgery uses plates and screws to restore and hold the alignment, giving the best chance of a well-functioning ankle and reducing the risk of later arthritis.
Restoring the joint surface accurately is the main goal.
Your choiceAre there alternatives in older adults?
The UK AIM trial showed that close contact casting can be a reasonable alternative to surgery for unstable ankle fractures in older patients, with similar function at six months and fewer wound problems.
This is one reason treatment is individualised, particularly where the skin and bone are fragile.
Getting backWhat is the recovery timeline?
There is often a period of limited or no weight-bearing followed by a boot, with full recovery over several months.
Your team will set out the stages for your fracture and fixation.
WellbeingWill I get arthritis later?
Any injury that disrupts a joint surface carries some long-term arthritis risk. Accurate realignment reduces, but does not entirely remove, that risk.
Most people walk well after a well-treated fracture.
UrgentWhat are the warning signs?
Severe escalating pain, numbness, cold toes, or wound discharge with a temperature need urgent review.
Calf swelling or breathlessness can signal a clot and needs urgent help.
References & further reading
- 1.NHS: Broken ankle
- 2.British Orthopaedic Foot & Ankle Society: Ankle arthritis patient information
- 3.Royal College of Surgeons of England: Driving after surgery guidance
References are to UK clinical guidance and patient information from recognised organisations. This page is for general information and does not replace personalised advice from your own clinical team.