01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Mechanism sets the differential. Inversion in plantar flexion usually injures lateral ligaments; eversion can injure deltoid structures; external rotation with dorsiflexion or a planted foot raises the syndesmosis. Ask whether the patient heard a crack, continued play, bore weight immediately and now, and whether pain sits below or above the ankle. Record previous sprains, instability, sport, anticoagulation, diabetes and neuropathy. High-energy trauma, deformity or neurological change bypasses routine assessment.
Expose the leg from knee to toes. Inspect swelling, bruising, wounds, alignment and threatened skin. Palpate posterior edges and tips of both malleoli, the full fibula including its head, syndesmosis, deltoid region, lateral ligaments, base of fifth metatarsal, navicular, midfoot, calcaneus and Achilles. Document dorsalis pedis and posterior tibial pulses, refill and superficial peroneal, deep peroneal, sural, saphenous and tibial sensory territories with key motor functions.
Ottawa rules reduce unnecessary radiographs when applied correctly to alert adults with acute injury. Ankle-zone pain plus posterior-edge or tip tenderness of either malleolus, or inability to bear weight for four steps both immediately and at assessment, requires ankle radiographs. Midfoot-zone pain plus navicular or fifth-metatarsal-base tenderness, or the same walking inability, requires foot films. Clinical judgement overrides the rule in neuropathy, intoxication, distracting injury, pregnancy discussion, delayed presentation or unreliable examination.
Syndesmotic injury deserves deliberate testing. Palpate from the anterior inferior tibiofibular ligament proximally and record the height of tenderness. External-rotation stress and compression of tibia and fibula higher in the calf may reproduce distal pain, but no single test excludes injury. Look for medial tenderness and proximal fibular pain. Weight-bearing mortise radiographs can reveal diastasis when tolerated; stress views require experienced pathways. MRI maps ligament injury when radiographs are normal yet suspicion and management consequence remain high.
For a stable lateral sprain, protect briefly with a brace or support, use compression and elevation for swelling and begin pain-limited weight-bearing. Early active dorsiflexion and plantar flexion, then calf and peroneal resistance and balance work improves recovery compared with prolonged immobilisation. A severe sprain may need several days of stronger support before the same functional path. Analgesia should facilitate walking and exercises, not produce a premature return to cutting sport.
A stable syndesmotic sprain usually needs longer protected weight-bearing and a boot or brace followed by staged rehabilitation. An unstable mortise, diastasis, fracture or proximal fibular pattern requires orthopaedic fixation planning. Syndesmotic screws or dynamic devices aim to restore fibular position; postoperative loading depends on construct and associated injury. Malreduction of even a small amount matters because it changes joint contact mechanics.
Review failure intelligently. Continued inability to bear weight, deep joint pain, locking, recurrent effusion or little improvement after one to two weeks warrants re-examination and possible repeat radiographs or MRI for occult fracture, osteochondral injury, tendon damage or syndesmosis. Recurrent giving way after healing needs mechanical laxity and neuromuscular assessment. Surgery for chronic lateral instability follows a structured rehabilitation trial and imaging that answers a repair or reconstruction question.
Pregnancy does not prohibit clinically indicated radiographs; optimise technique and discuss analgesia. Older adults and neuropathic patients may fracture with low energy and under-report pain. Anticoagulation increases bruising but does not explain bony tenderness or instability. Any lower-limb immobilisation requires VTE and pressure-area assessment. Return to sport requires pain-controlled running, near-symmetrical strength and balance, hopping, landing and change of direction, not merely reduced swelling.
Key points
- Do not begin with the label sprain: inspect deformity and skin, document pulses and nerves, palpate the entire fibula, malleoli, navicular, fifth-metatarsal base and Achilles, then test function.
- Use the Ottawa ankle and foot rules to decide first-line radiography in alert adults: posterior malleolar, navicular or fifth-base tenderness or inability to take four steps warrants films.
- Lateral sprain produces tenderness over the anterior talofibular and sometimes calcaneofibular ligaments; delayed anterior drawer or talar tilt may be more informative after acute guarding settles.
- Syndesmotic injury causes pain above the mortise with external rotation, dorsiflexion or calf squeeze and often a slower recovery than an ordinary lateral sprain.
- First-line management of an uncomplicated lateral sprain is short protection, compression and elevation followed promptly by weight-bearing as tolerated, range, strength and balance rehabilitation.
- First-line imaging for suspected unstable syndesmosis is weight-bearing ankle radiography when safe, with full-length tibia-fibula views for proximal tenderness; MRI is the reference soft-tissue test when instability remains uncertain.
- Restrict weight-bearing and arrange urgent orthopaedic review when syndesmotic diastasis, associated fracture, deltoid disruption or marked clinical instability is suspected; fixation may be required.
- Prevent recurrence with progressive peroneal and calf strength, dorsiflexion, balance, hopping and sport-specific change-of-direction work, adding taping or a brace for higher-risk return.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Inversion plantar-flexion injury
Most lateral sprains follow inversion in plantar flexion, injuring the anterior talofibular ligament first and the calcaneofibular ligament with greater force.
External-rotation dorsiflexion injury
Syndesmotic injury occurs when the talus externally rotates within the mortise or forces tibia and fibula apart during dorsiflexion.
Eversion and medial injury
Eversion can injure the deltoid ligament and should raise suspicion for associated syndesmotic disruption or proximal fibular fracture.
Recurrent instability susceptibility
Previous sprain, impaired balance, reduced dorsiflexion, inadequate rehabilitation and return before neuromuscular recovery increase recurrence risk.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Lateral ligament fibre injury
Microscopic stretch through partial or complete ligament failure causes bleeding, swelling and pain, while joint congruity often remains stable enough for functional treatment.
- 2Syndesmotic mortise widening
Failure of the anterior and posterior tibiofibular ligaments and interosseous structures permits abnormal fibular movement and increases tibiotalar contact stress.
- 3Proprioceptive impairment
Ligament mechanoreceptor disruption and pain reduce balance and peroneal response, explaining recurrent giving way after swelling has resolved.
- 4Chondral and impingement injury
Rotational trauma can damage talar cartilage or create synovitis and scar, producing persistent deep pain, catching or anterolateral impingement.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Tenderness below the lateral malleolus over the anterior talofibular ligament, with inversion mechanism and local swelling, supports lateral sprain.
Pain above the mortise during external rotation, dorsiflexion or calf squeeze and tenderness extending proximally identifies a high-ankle pattern.
Proximal fibular pain or tenderness accompanying medial or syndesmotic ankle findings signals a rotational fracture pattern beyond the ankle image.
Posterior malleolar-edge, navicular or fifth-metatarsal-base tenderness and inability to walk four steps determine the first radiographic pathway.
Deep pain, recurrent swelling, catching or locking that persists beyond expected ligament recovery raises a talar dome lesion.
Deformity, skin tenting, open wound, absent pulse or progressive sensory-motor deficit requires immediate reduction and specialist trauma care.
05InvestigationsWhat to request, why it matters and how to interpret it.
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
First-line Ottawa-rule assessmentFirst stepFirst line - Why
- Select patients who need ankle or foot radiographs after acute injury while screening for rule exclusions.
- Interpretation and limitations
- Any qualifying bony tenderness or four-step inability warrants imaging; unreliable examination or high-risk context needs clinical judgement beyond the rule.
- 02
First-line ankle and foot radiographs when indicatedFirst line - Why
- Detect malleolar, talar, fifth-metatarsal, navicular and alignment injury.
- Interpretation and limitations
- Obtain appropriate orthogonal and mortise views; a normal non-weight-bearing film does not exclude syndesmotic instability or occult osteochondral injury.
- 03
Weight-bearing mortise radiographs for syndesmosis - Why
- Assess tibiofibular relationship and medial clear space under physiological load when safe.
- Interpretation and limitations
- Widening indicates instability; normal measurements do not fully exclude ligament injury when examination remains strongly suggestive.
- 04
Full-length tibia-fibula radiographs - Why
- Identify proximal fibular fracture and the complete injury pattern when proximal tenderness or medial-syndesmotic signs are present.
- Interpretation and limitations
- Ankle-only imaging can miss a Maisonneuve fracture, so image the tender proximal segment and assess the knee.
- 05
MRI for persistent or high-grade soft-tissue concern - Why
- Define syndesmotic ligaments, talar cartilage, occult fracture and peroneal tendon injury when results change management.
- Interpretation and limitations
- MRI is the reference soft-tissue investigation but should follow acute protection and not delay urgent treatment of obvious instability.
- 06
CT for fracture or operative anatomy - Why
- Map posterior malleolus, complex fracture and syndesmotic reduction when cross-sectional bone detail affects fixation.
- Interpretation and limitations
- CT complements rather than replaces weight-bearing stability assessment and specialist interpretation.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Ankle or foot fracture
Posterior malleolar-edge, navicular or fifth-metatarsal-base tenderness and inability to walk require fracture imaging under Ottawa criteria.
Maisonneuve injury
Proximal fibular tenderness with medial or syndesmotic ankle pain indicates a long rotational injury that may be missed by ankle-only radiographs.
Osteochondral talar lesion
Persistent deep joint pain, swelling, catching or locking after the expected sprain recovery supports cartilage and subchondral imaging.
Peroneal tendon injury
Posterolateral pain, snapping behind the fibula or weakness on eversion suggests tendon tear or retinacular disruption.
Achilles rupture
A posterior pop, weak push-off, altered resting angle and abnormal calf-squeeze test identifies tendon discontinuity rather than ligament sprain.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01First-lineExclude fracture and limb threatFirst stepFirst lineAn acute ankle injury presents without immediate need for trauma resuscitation.+
- 1Inspect skin and alignment and document pulses, refill, sensation and motor function before stress testing.
- 2Apply Ottawa criteria, palpate the entire fibula and assess Achilles, midfoot and fifth-metatarsal base.
- 3Obtain ankle, foot or full-leg radiographs according to the anatomical findings and restrict loading until important injury is excluded.
- 4EscalationReduce and escalate immediately for deformity, threatened skin or neurovascular compromise rather than waiting for routine imaging.
02Lateral sprainMove early after brief protectionFracture and unstable syndesmotic injury are unlikely and the pattern is an isolated stable lateral sprain.+
- 1Use a supportive brace, compression, elevation and compatible analgesia, allowing weight-bearing as pain permits.
- 2Begin ankle range promptly, then progress calf and peroneal strength and single-leg balance.
- 3Advance to hopping, landing and change-of-direction tasks before full sport or hazardous work.
- 4Reassess in one to two weeks if weight-bearing and function are not improving or if locking and deep pain emerge.
03SyndesmosisDetermine mortise stabilityPain lies above the ankle, provocative tests reproduce it or medial and proximal fibular findings coexist.+
- 1Restrict weight-bearing, support the ankle and obtain weight-bearing mortise views when safe plus full-length fibular imaging when indicated.
- 2Arrange early orthopaedic review and MRI when radiographs are normal but clinically important syndesmotic injury remains likely.
- 3Treat a stable injury with longer protected rehabilitation and objective progression than a routine lateral sprain.
- 4Plan fixation for diastasis, unstable stress imaging or associated fracture, followed by construct-specific weight-bearing and rehabilitation.
04Persistent symptomsReopen the diagnosisPain, swelling, locking or instability does not follow the expected recovery trajectory.+
- 1Repeat bony, syndesmotic, tendon and neurovascular examination and review whether initial films were weight-bearing and anatomically complete.
- 2Use repeat radiographs, MRI or CT for occult fracture, talar osteochondral lesion, tendon injury, impingement or malreduced syndesmosis.
- 3Complete a structured strength and proprioception programme before labelling chronic lateral instability surgical.
- 4Refer recurrent mechanical giving way, confirmed cartilage injury or syndesmotic instability to the appropriate foot-and-ankle service.
Key medicines and prescribing safety3 treatments · regimens, roles and cautions+
Paracetamol for acute ankle pain
Use 500–1000 mg orally as required, leaving 4 hours or longer between doses and limiting the 24-hour total to 4 g; lower that ceiling for low body weight, frailty, malnutrition or liver risk.Check all combination products and alcohol or hepatic risk; analgesia does not make an unstable mortise safe to load.
Topical diclofenac gel
Spread 2–4 g of diclofenac 1.16% gel over intact painful ankle skin per application, up to three or four times daily for a brief course within the licensed maximum.Avoid wounds, significant skin abrasion and NSAID hypersensitivity, account for other NSAIDs and pregnancy, and do not conceal worsening compartment or infection pain.
Oral naproxen with gastroprotection when appropriate
For a suitable adult, prescribe oral naproxen 250–500 mg with food two times daily, for only the briefest effective period; add omeprazole 20 mg once per day when gastroprotection is indicated.Review ulcer and bleed history, renal function, heart failure, hypertension, cardiovascular risk, anticoagulants and antiplatelets; avoid combined NSAIDs and follow pregnancy restrictions from 20 weeks.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Chronic lateral instability
Recurrent giving way follows mechanical laxity, proprioceptive loss and incomplete strength recovery, leading to repeated sprains and activity restriction.
Syndesmotic malreduction
Unrecognised instability changes ankle mortise mechanics and progressively accelerates pain, cartilage loss and post-traumatic osteoarthritis development.
Persistent stiffness and impingement
Prolonged immobilisation or scar can restrict functional dorsiflexion, while synovial thickening creates painful anterolateral pinching symptoms.
Missed osteochondral injury
Talar dome damage can cause chronic swelling, catching and deep load pain despite apparently healed lateral ligaments.
Thrombosis and pressure injury
Reduced mobility, casting and poorly fitted braces add venous-thromboembolism and skin risk, especially with comorbidity or prolonged protection.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Recheck skin, swelling, pulses, sensation and motor function after bracing or casting and whenever pain escalates.
- Track four-step weight-bearing, ankle range, tenderness height and ability to perform a controlled single-leg stance.
- For syndesmosis, confirm radiographic alignment and follow the specialist weight-bearing schedule rather than a routine sprain timetable.
- Review persistent effusion, deep pain, catching or locking for talar osteochondral injury and occult fracture.
- Measure peroneal and calf strength, balance, hopping and change-of-direction control before return to sport.
- During immobilisation, reassess VTE risk, skin pressure, falls and safe mobility aids, providing urgent thrombosis advice.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Palpate the knee in ankle trauma
Rotational force can fracture the proximal fibula while symptoms focus at the ankle, so an ankle-only examination and film can miss instability.
Ottawa rules choose radiographs
They do not grade ligament injury, clear syndesmosis or replace clinical judgement in neuropathy and unreliable examination.
High sprains recover slowly
Syndesmotic load occurs throughout stance and rotation, so apparently modest swelling can accompany prolonged functional limitation.
Weight bearing can reveal instability
A non-weight-bearing mortise may look normal when load exposes tibiofibular widening; obtain physiological views only when safe.
Balance prevents the next sprain
Ligament healing does not automatically restore proprioception or rapid peroneal response, making neuromuscular training central to recurrence prevention.
Persistent swelling needs a question
Recurrent effusion, catching or focal deep pain should trigger assessment for cartilage, occult fracture or impingement rather than endless rest.
11Common pitfallsFrequent interpretation and management errors.
- 01
Calling the injury a sprain before documenting skin, circulation, nerves and Ottawa bony findings.
- 02
Examining only the ankle and missing proximal fibular tenderness in a Maisonneuve injury.
- 03
Using one negative squeeze or external-rotation test to exclude syndesmotic disruption.
- 04
Immobilising every lateral sprain for weeks instead of progressing early functional rehabilitation.
- 05
Treating a high-ankle sprain on the same rapid return timetable as a mild lateral injury.
- 06
Ignoring deep pain, locking and recurrent effusion after the expected recovery window.