Ankle fracture and Ottawa ankle rules

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Take a precise mechanism and functional history. Establish foot position, rotation, fall height, immediate ability to walk, previous neuropathy, diabetes, smoking, vascular disease, anticoagulation and baseline mobility. Inspect the full leg before compressing swollen tissue. Record wounds, blisters, medial skin tenting and deformity. Palpate the posterior edge and tip of each malleolus, navicular, fifth-metatarsal base, entire fibula and proximal tibiofibular region, then assess Achilles continuity and midfoot stability.

The Ottawa rules safely reduce unnecessary imaging when their entry conditions and landmarks are used exactly. The ankle rule applies to malleolar-zone pain and is positive for posterior-edge or tip tenderness over the distal six centimetres of either malleolus, or inability to take four steps both immediately after injury and at assessment. The foot rule applies to midfoot-zone pain and is positive for navicular or fifth-metatarsal-base tenderness or the same walking criterion. NICE recommends their use in adults and children over five.

Decision rules have boundaries. They do not classify fracture stability, exclude a proximal fibular injury or assess tendons, skin and circulation. Intoxication, altered sensation, distracting injury, inability to communicate or presentation outside the validated acute setting reduces reliability and favours clinical judgement. Persistent focal pain or inability to progress despite a negative study needs planned review and sometimes repeat or alternative imaging rather than false reassurance.

When imaging is indicated, obtain AP, mortise and lateral ankle views with adequate positioning. Look for fibular level and length, medial clear-space widening, talar shift, posterior malleolar involvement, syndesmotic widening and osteochondral injury. Image the full tibia and fibula for proximal tenderness or suspicious syndesmotic findings. CT is useful for complex posterior malleolar, plafond and comminuted injuries and after provisional reduction when it affects fixation; MRI is selective for occult fracture, tendon or ligament questions.

Reduction precedes perfect imaging when skin or circulation is threatened. Give analgesia and appropriate sedation or regional anaesthesia with monitoring, apply longitudinal traction and reverse the deforming mechanism, then maintain reduction in a well-padded backslab or equivalent splint. Check and record pulses, capillary refill and named nerve function before and after. Obtain post-reduction radiographs, elevate while protecting perfusion and recheck skin as swelling evolves. Failed or unstable reduction needs immediate orthopaedic action.

Management depends on stability, alignment, soft tissues and the person. An isolated stable unimalleolar fracture without talar shift can often bear weight as tolerated in a boot or cast with fracture-clinic review. An unstable pattern includes talar shift, bimalleolar or trimalleolar injury, a bimalleolar equivalent, syndesmotic disruption or loss of reduction. These usually require fixation once skin permits; temporary spanning fixation may be needed for severe swelling, plafond injury or persistent instability.

Rehabilitation begins with a written plan: loading status, device, ankle and toe movement, elevation, skin checks, analgesia and review date. Assess VTE and bleeding risk for immobilisation under NICE NG89 and consider pharmacological prophylaxis when thrombosis risk outweighs bleeding risk, generally stopping if immobilisation continues beyond forty-two days. Follow radiographic alignment in injuries at risk of displacement and monitor wound, union, dorsiflexion, calf strength, balance and return to work or sport.

Key points

Inspect before palpation: gross deformity, threatened medial skin, open wound or neurovascular compromise takes priority over applying a decision rule or obtaining ideal radiographs.
In people older than 5 years with traumatic ankle or midfoot pain, NICE recommends the Ottawa ankle and foot rules to decide whether radiographs are needed.
Request ankle radiographs for posterior-edge or tip tenderness over the distal 6 cm of either malleolus, or inability to take four steps both immediately after injury and during assessment.
Request foot radiographs for navicular or base-of-fifth-metatarsal tenderness, or the same inability to take four steps, when pain lies in the midfoot zone.
The Ottawa rules decide imaging, not discharge, stability or treatment; they do not replace examination for wounds, proximal fibular pain, tendon rupture, neurovascular deficit or compartment syndrome.
Obtain AP, mortise and lateral ankle radiographs when indicated; include the whole tibia and fibula for proximal tenderness, and use CT when posterior malleolar, plafond or complex fracture anatomy will change management.
Urgently reduce a fracture-dislocation with threatened skin or circulation, then document neurovascular findings and obtain post-reduction films; do not wait for CT.
Stable unimalleolar injuries may use a boot or cast with early loading and review, while talar shift, bimalleolar-equivalent, syndesmotic or displaced multi-malleolar patterns need urgent operative assessment.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Rotational low-energy trauma

Twisting during a fall or sport commonly produces sequential malleolar and ligament failure according to foot position and force direction.

High-energy axial load

Road collision or fall from height produces comminution, plafond involvement, open wounds and wider soft-tissue damage than a simple rotational injury.

Fragility fracture

Osteoporosis, frailty and falls allow low-energy ankle fracture, often with swelling, skin vulnerability and rehabilitation needs that complicate operative decisions.

Neuropathic injury

Diabetes and loss of protective sensation permit unrecognised displacement, skin breakdown and Charcot-like collapse, increasing fixation and infection risk.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Mortise instability
Failure of malleoli, deltoid ligament or syndesmosis permits talar shift within the mortise; small displacement markedly alters contact pressure and cartilage loading.
2
Sequential ring failure
The ankle behaves as a bony-ligament ring, so an apparent single break should prompt a search for a second osseous or ligamentous lesion.
3
Skin pressure injury
Displaced bone presses against thin swollen ankle skin, compromising perfusion and converting a closed injury into necrosis or open breakdown.
4
Post-traumatic degeneration
Residual incongruity, talar tilt, syndesmotic malreduction and cartilage impact lead to chronic pain, stiffness and ankle osteoarthritis.
5
Immobilisation effects
Pain, casting and restricted loading cause calf wasting, stiffness and venous stasis, while excessive early movement can displace an unstable pattern.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Stable unimalleolar pattern

An isolated, acceptably aligned malleolar fracture with a congruent mortise and no clinical or radiographic evidence of deltoid or syndesmotic failure may remain stable under load.

Bimalleolar equivalent

A fibular fracture with medial tenderness or clear-space widening can represent deltoid rupture even when the medial malleolus is intact.

Trimalleolar injury

Medial and lateral fractures plus a posterior tibial fragment often reflects greater rotational energy, instability and a need for CT-defined fixation planning.

Maisonneuve pattern

Medial ankle injury and syndesmotic disruption with a proximal fibular fracture demands whole-leg imaging and assessment of common fibular nerve function.

Pilon or plafond injury

Axial load causes distal tibial articular comminution, marked swelling and fracture blisters; staged soft-tissue-safe reconstruction differs from routine ankle fixation.

Threatened skin

Blanching, tenting or loss of sensation over a displaced malleolus indicates pressure ischaemia and triggers immediate reduction before prolonged imaging.

Red flags requiring action

A tented, blanched or insensate skin bridge over a displaced malleolus, absent pulses, cool foot or gross fracture-dislocation requires immediate reduction and reassessment before routine imaging.
Any wound near a fracture, exposed bone, contamination or gas in tissue is an open fracture until specialist assessment proves otherwise and needs the formal open-fracture pathway.
Pain escalating despite reduction, pain on passive toe movement, tense swelling or progressive sensory or motor loss raises acute compartment syndrome and requires emergency review.
Proximal fibular tenderness or common fibular nerve symptoms with ankle pain suggests a Maisonneuve pattern and unstable syndesmotic injury that a focal ankle film can miss.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Ottawa ankle and foot rulesFirst step
Why
Select patients with acute ankle or midfoot trauma who need radiography.
Interpretation and limitations
A positive age-appropriate rule triggers the relevant films; a negative rule does not assess instability, tendon injury, proximal fibula, wounds or neurovascular status.
02
First-line ankle radiographsFirst line
Why
Define malleolar fracture and mortise alignment.
Interpretation and limitations
Use AP, mortise and lateral views; review talar shift, medial clear space, fibular length, posterior fragment, plafond and any associated avulsion.
03
Foot or full-leg radiographs
Why
Find linked ring injuries outside the immediate ankle field.
Interpretation and limitations
Obtain foot views for a positive Ottawa foot rule and full tibia-fibula views for proximal tenderness or suspected Maisonneuve injury.
04
Post-reduction radiographs
Why
Confirm that the talus and fragments are acceptably aligned in the splint.
Interpretation and limitations
Image after urgent reduction and compare the mortise, but repeat immediately if skin, circulation or neurology deteriorates rather than relying on the film.
05
CT ankle
Why
Map posterior malleolar, plafond and complex intra-articular anatomy.
Interpretation and limitations
Use when fragment morphology and incisural involvement alter fixation; CT follows emergency reduction and should not delay treatment of threatened skin.
06
Weight-bearing radiographs
Why
Assess functional mortise stability in selected uncertain injuries.
Interpretation and limitations
Only obtain through a specialist pathway when pain and safety permit; stress or weight-bearing interpretation depends on technique and clinical context.
07
Targeted MRI or ultrasound
Why
Investigate occult osteochondral, ligament or tendon pathology.
Interpretation and limitations
Reserve for persistent symptoms or a specific unanswered question after appropriate radiographs; it is not routine before reducing a fracture-dislocation.
08
Pre-operative assessment
Why
Identify bleeding, metabolic and anaesthetic factors without delaying reduction.
Interpretation and limitations
Use targeted FBC, renal profile, coagulation, group and screen, glucose and ECG according to injury, age, diabetes and anticoagulants.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Severe ankle sprain

Ligament rupture causes swelling and inability to load but may preserve bony alignment; instability and occult avulsion still require structured assessment.

Talar or calcaneal fracture

Hindfoot tenderness, axial-load mechanism or subtalar pain can indicate injuries not fully shown on standard ankle radiographs.

Maisonneuve injury

Proximal fibular fracture with syndesmotic and medial ankle disruption may cause modest ankle tenderness but represents an unstable ring injury.

Achilles tendon rupture

Posterior pain, palpable gap and abnormal calf-squeeze response cause impaired push-off without a malleolar fracture pattern.

Crystal or septic arthritis

Atraumatic hot swollen ankle with fever or systemic illness needs urgent inflammatory and aspiration assessment rather than a trauma-only pathway.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01ImmediateReduce skin or circulation threatFirst stepThe ankle is grossly deformed, open, neurovascularly compromised or tenting the skin.

1Perform trauma assessment, expose and photograph wounds once under policy, document pulses and named nerve function and give analgesia.
2EscalationCover an open wound and give immediate network intravenous prophylaxis while preparing urgent reduction and orthopaedic escalation.
3Reduce the deformity without waiting for ideal films when skin or perfusion is threatened, then apply a well-padded splint.
4EscalationRepeat skin and neurovascular examination, obtain post-reduction imaging and escalate failed, unstable or deteriorating reduction immediately.

02StableProtect while restoring movementThe mortise is congruent and the fracture or ligament injury is judged stable after adequate imaging.

1Provide a boot, cast or brace with explicit weight-bearing and ankle-movement instructions and ensure safe crutch use.
2Arrange timely fracture-clinic review and repeat weight-bearing or standard radiographs when stability remains uncertain.
3Use elevation, skin surveillance and progressive range and strengthening while avoiding prolonged unnecessary immobilisation.
4Assess VTE risk, falls and bone health and provide clear return advice for displacement, pressure damage or thrombotic symptoms.

03UnstableRestore and maintain the mortiseTalar shift, multi-malleolar injury, syndesmotic failure, plafond involvement or recurrent displacement is present.

1Maintain a safe reduction and allow swollen or blistered skin to recover, using spanning fixation if a splint cannot protect alignment or tissue.
2Use CT when posterior or plafond morphology changes operative approach and plan fibular, medial, posterior and syndesmotic stabilization together.
3Fix once soft tissue and physiology permit and document postoperative loading, movement, wound and thromboprophylaxis instructions.
4EscalationMonitor radiographic congruity, wound healing, union and function, escalating infection, loss of reduction or neuropathic collapse early.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

Provides baseline analgesia for examination, reduction recovery and early safe mobilisation with less sedation than escalating opioid alone.

Paracetamol

Give 1 g orally up to four times daily as required, leaving at least 4 hours between doses and not exceeding 4 g in 24 hours; reduce the maximum for low body weight, frailty, malnutrition or hepatic risk.

Count all combination products and consider alcohol and liver disease; analgesia must accompany rather than postpone reduction of threatened skin or reassessment of increasing pressure pain.

Reduces immobilisation-related venous thromboembolism when predicted thrombosis risk exceeds bleeding risk.

Low-molecular-weight heparin for selected lower-limb immobilisation

When individual VTE assessment favours prophylaxis, prescribe the locally selected low-molecular-weight heparin at its licensed prophylactic dose adjusted for renal function and weight, continuing for the planned immobilisation period and considering cessation if immobilisation exceeds 42 days.

There is no universal prescription for every ankle injury; check bleeding, platelets, renal function, pregnancy, interacting anticoagulants and procedural or neuraxial timing, and record the review or stop date.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Skin necrosis and infection

Delayed reduction, open injury, fracture blisters, diabetes and poorly timed surgery increase wound breakdown, deep infection and implant exposure.

Malunion and arthritis

Persistent talar shift, fibular shortening or syndesmotic malreduction causes instability, altered joint loading and progressive post-traumatic osteoarthritis.

Fixation or union failure

Poor biology, smoking, neuropathy, infection and premature unprotected loading can cause loss of reduction, nonunion or implant failure.

Stiffness and chronic pain

Prolonged immobilisation, cartilage injury and complex regional pain produce limited dorsiflexion, weakness and impaired gait after bony union.

Venous thromboembolism

Lower-limb immobilisation and reduced weight bearing increase thrombosis risk, which must be balanced against bleeding when deciding prophylaxis.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Repeat skin colour, sensation, blisters, wounds, pulses, capillary refill and named nerve function after reduction, splinting and any pain or swelling change.
Check splint or cast pressure, fit and integrity and provide direct return instructions for increasing pain, numbness, wetness, odour or toe colour change.
Use scheduled radiographs to confirm maintenance of mortise alignment and syndesmotic relationship before changing loading or support.
Review wound and implant sites after surgery and escalate drainage, spreading erythema, fever, dehiscence or disproportionate pain.
Track dorsiflexion, plantarflexion, calf strength, balance, gait and patient-relevant work or sport function rather than radiographic union alone.
Reassess VTE and bleeding risk when mobility, surgery, contraception, pregnancy, cancer or anticoagulation status changes.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Ottawa selects imaging

A negative rule can avoid radiography in an eligible patient, but it neither labels an injury a sprain nor proves functional stability.

Palpate the fibular head

Syndesmotic force can travel proximally and produce a Maisonneuve fracture beyond the ankle radiographic field.

Reduce before CT

Restoring talar position protects skin and cartilage and makes later cross-sectional assessment more clinically useful.

Posterior size is incomplete

Posterior malleolar fixation decisions also depend on morphology, incisural involvement, impaction and syndesmotic stability rather than fragment percentage alone.

Neuropathy changes thresholds

Loss of protective sensation can mask displacement and cast pressure while increasing fixation failure, infection and Charcot collapse risk.

Weight-bearing must be explicit

Terms such as partial weight bearing are difficult to reproduce; write the permitted load, device and progression linked to review.

11Common pitfallsFrequent interpretation and management errors.

01
Applying Ottawa criteria to a visibly deformed or skin-threatening ankle instead of treating the emergency first.
02
Palpating only the distal fibula and missing a proximal Maisonneuve fracture and common fibular nerve deficit.
03
Calling an isolated fibular fracture stable without assessing medial tenderness, mortise congruity and syndesmotic injury.
04
Waiting for CT before reducing a fracture-dislocation that is compromising skin or circulation.
05
Discharging in a cast without recorded neurovascular findings, pressure advice, VTE decision and scheduled review.
06
Advancing load based only on elapsed weeks despite wound, alignment, pain or union concerns.