Lateral Ankle Sprains
Inversion Injury | ATFL Rupture | Brostrom-Gould Repair
Injury Grading
Critical Must-Knows
- ATFL is injured first in plantarflexion (weakest position)
- Ottawa Ankle Rules reduce unnecessary X-rays by 30-40%
- Functional rehab is superior to immobilization (Cochrane)
- Brostrom-Gould repair is the Gold Standard for chronic instability
- Rule out associated injuries: Maisonneuve, Base 5th MT, Osteochondral lesion
Clinical Pearls
- "Don't offer surgery for acute sprains (even Grade III) - evidence supports conservation
- "Identify 'Mechanical' vs 'Functional' instability
- "Always palpate the proximal fibula (Maisonneuve fracture)
- "Prophylactic bracing reduces re-injury by 50%
Clinical Imaging
Imaging Gallery


Critical Exam Points
Ottawa Rules
Mandatory Knowledge. Know the 5 zones: Posterior edge/tip Lateral Malleolus, Medial Malleolus, Navicular, Base 5th MT, Weight bearing 4 steps.
Acute Management
Conservative First. Grade III acute ruptures heal well with functional rehab. Surgery is reserved for CHRONIC instability.
Must Not Miss
Associated Fractures. Maisonneuve (proximal fibula), Jones (Base 5th), Lisfranc (midfoot), Osteochondral lesion of Talus.
Surgical Standard
Brostrom-Gould. Anatomic repair of ATFL/CFL with retinaculum reinforcement. Avoid non-anatomic tenodesis.
At a Glance: Differential Diagnosis
| Condition | Key Feature | Test | Management |
|---|---|---|---|
| Lateral Ankle Sprain | Inversion mech + ATFL tenderness | Anterior Drawer | Functional Rehab |
| Syndesmosis Injury | High ankle pain, dorsiflexion pain | Squeeze Test | Boot/TightRope |
| Fracture (Weber B) | Bony tenderness, unable to WB | X-ray (Ottawa) | ORIF vs Boot |
| Peroneal Dislocation | Snap/Pop, tendon subluxes | Resisted Eversion | Repair Retinaculum |
| Osteochondral Lesion | Deep pain, locking, persistent effusion | MRI | Debridement/Fixation |
AFPLigament Injury Sequence
| A | Anterior Talofibular (ATFL) First to tear (Plantarflexion) |
| F | Fibular Calcaneal (CFL) Second to tear (Neutral/Dorsiflexion) |
| P | Posterior Talofibular (PTFL) Last to tear (Dislocation) |
| A | Anterior Talofibular (ATFL) First to tear (Plantarflexion) |
| F | Fibular Calcaneal (CFL) Second to tear (Neutral/Dorsiflexion) |
| P | Posterior Talofibular (PTFL) Last to tear (Dislocation) |
Hook:Anterior First in Plantarflexion.
Overview and Epidemiology
Lateral ankle sprains are the single most common musculoskeletal injury. While most heal uneventfully, a significant minority develop Chronic Ankle Instability (CAI), leading to recurrent giving way, pain, and potential post-traumatic arthritis.
Pathophysiology and Mechanisms
ATFL (Weakest Link)
- Origin: Anterior distal fibula
- Insertion: Lateral talar neck
- Function: Resists anterior translation + inversion in plantarflexion
- Thickness: Only 2mm (often just capsular thickening)
- Injury: 85-90% of sprains
CFL (Stabilizer)
- Origin: Fibula tip
- Insertion: Lateral calcaneus
- Function: Resists inversion in neutral/dorsiflexion
- Course: Deep to peroneal tendons
- Injury: 50-75% of severe sprains (usually with ATFL)
Critical Zone
The ankle is least stable in Plantarflexion. The wider anterior talus exits the mortise, relying entirely on ligaments (ATFL) for stability. This is why landing from a jump (plantarflexed foot) is the classic mechanism.
Classification Systems
Clinical Grading (Amalgamated)
| Grade | Pathology | Clinical Findings | Stability | Rest |
|---|---|---|---|---|
| I (Mild) | Microscopic tear | Mild swelling, WB tolerated | Stable | 1-2 weeks |
| II (Moderate) | Partial macroscopic tear | Moderate swelling, limp | Mild laxity | 2-6 weeks |
| III (Severe) | Complete rupture | Severe swelling, Non-WB | Gross instability | 6-12 weeks |
Clinical Assessment
CAMP BOttawa Ankle Rules (X-ray Indications)
| C | Cannot weight bear 4 steps immediately & in ED |
| A | Anterior/Posterior Malleoli Tenderness distal 6cm |
| M | Medial Malleolus Tenderness tip/posterior edge |
| P | Posterior edge Lateral Malleolus Tenderness tip/posterior edge |
| B | Base of 5th MT / Navicular Foot tenderness zones |
| C | Cannot weight bear 4 steps immediately & in ED | P | Posterior edge Lateral Malleolus Tenderness tip/posterior edge |
| A | Anterior/Posterior Malleoli Tenderness distal 6cm | B | Base of 5th MT / Navicular Foot tenderness zones |
| M | Medial Malleolus Tenderness tip/posterior edge |
Hook:Set up CAMP at the BASE of the mountain.
Examination Sequence
Egg-shaped swelling over lateral malleolus (Haematoma sign). Check specifically for 'Too Many Toes' signs (pes planovalgus predisposes to instability).
Rules out fractures: Fibula tip, Medial Mall, Base 5th MT, Navicular, Proximal Fibula (Maisonneuve).
Anterior Drawer: Tests ATFL. (Positive greater than 3mm diff). Talar Tilt: Tests CFL. (Positive greater than 10deg or greater than 5deg diff). Squeeze Test: Syndesmosis.
Investigations
Standard Views: AP, Lateral, Mortise. Indications: Ottawa positive, inability to weight bear, high impact.
Management Algorithm

Acute Management Gold Standard: Functional Rehabilitation (early motion + bracing) is superior to cast immobilization (Cochrane 2012). Immobilization should be reserved for severe pain or fractures, and limited to less than 10 days.
Surgical Technique
Modified Brostrom-Gould Repair
The Gold Standard Anatomic Repair.
Steps
Curvilinear incision anterior to fibula. Protect Superficial Peroneal Nerve (SPN) anteriorly.
Open capsule. Identify widely stretched/torn ATFL/CFL remnants. Debride edges.
Place suture anchors (or transosseous tunnels) in distal fibula. Plicate ATFL/CFL in pants-over-vest fashion. Tighten in slight eversion/dorsiflexion.
Mobilize Inferior Extensor Retinaculum. Advance superiorly over the repair. Increases strength and limits inversion (check subtalar motion).

Complications
Nerve Injury
- Superficial Peroneal Nerve: Most common (5-10%). Crossing branches in subcutaneous tissue.
- Sural Nerve: Risk with posterior dissection for CFL.
Recurrence
- Instability: 5-10% failure rate.
- Stiffness: Overtightening causes loss of inversion/subtalar motion.
Wound
- Dehiscence: Thin skin over lateral malleolus.
- Infection: less than 1%.
Missed Pathology
- Persistent Pain: Missed OCL, sinus tarsi syndrome, or peroneal tear.
Postoperative Care
Rehab Protocol
Backslab/Moonboot. Non-weight bearing or PWB. Wound healing priority.
CAM Boot. Start ROM (dorsiflexion/plantarflexion). Avoid inversion. Peroneal strengthening.
Lace-up brace. Proprioception training (balance board). Progress to jogging.
Sport-specific drills. Pass functional tests (Hop test).
PMSFRehab Phases
| P | Protection 0-2 wks: Boot, RICE |
| M | Motion 2-4 wks: ROM, Isometric |
| S | Strengthening 4-6 wks: Peroneals, Balance |
| F | Function 6+ wks: Plyometrics, Sport |
| P | Protection 0-2 wks: Boot, RICE | S | Strengthening 4-6 wks: Peroneals, Balance |
| M | Motion 2-4 wks: ROM, Isometric | F | Function 6+ wks: Plyometrics, Sport |
Hook:Please Make Sure Function returns.
Outcomes and Prognosis
| Treatment | Success Rate | Return to Sport | Complications |
|---|---|---|---|
| Functional Rehab (Acute) | 80-90% | 2-6 weeks | 20% Chronic Instability |
| Brostrom Repair | 90-95% | 3-4 months | 5% Nerve Injury |
| Tenodesis (Non-anatomic) | 70-80% | 4-6 months | Stiffness/DJD |
Controversies & Areas of Uncertainty
Arthroscopic vs Open Brostrom
Arthroscopic repair shows comparable stability with faster early weightbearing, but there are no long-term trials. Open Brostrom-Gould remains the reference standard until durable data emerge.
Internal Brace / Suture Tape
Augmentation may permit accelerated rehabilitation and protect weak tissue, but adds cost and a non-anatomic, stiffer construct. Best evidence is for revision, hyperlaxity, high-demand athletes and obesity, not routine primary repair.
Surgery After Acute Grade III
Pihlajamaki's RCT showed lower reinjury after acute repair but more osteoarthritis. The balance of evidence still favours functional treatment first, with surgery reserved for failure.
Routine MRI
MRI is over-used acutely. It is reserved for persistent pain (over 6 weeks), suspected osteochondral lesion or peroneal pathology, and pre-operative planning, not for diagnosing a simple sprain.
Evidence Base
Functional Treatment vs Immobilisation (Cochrane)
- 21 trials, 2184 participants; functional treatment favoured over immobilisation
- More patients returned to sport long-term (RR 1.86, 95% CI 1.22-2.86) and returned to work sooner (WMD 8.2 days)
- Less persistent swelling and less objective instability on stress X-ray with functional treatment
- Caveat: several differences lose significance when low-quality trials are excluded; this Cochrane review has since been withdrawn pending update, but its functional-over-immobilisation conclusion remains consistent with current society guidance
Anatomic Repair vs Tenodesis (RCT)
- Prospective randomised trial of 40 patients with chronic lateral instability
- Both procedures gave good or excellent stability in over 80% of patients
- Modified Brostrom achieved significantly higher Sefton functional scores than Chrisman-Snook
- Significantly more complications occurred after the non-anatomic Chrisman-Snook tenodesis
Prevention of Recurrent Ankle Sprains
- Critical review of 24 studies on ankle sprain prevention
- Taping, bracing and neuromuscular training all reduce recurrence (relative risks 0.2-0.5 vs control)
- Benefit is driven by previously injured athletes; effect on first-ever sprains is minimal
- Combining an external support (tape or brace) with neuromuscular training gives the best protection
Acute Surgery vs Functional Treatment (RCT)
- RCT of 51 young active men with acute Grade III rupture; mean 14-year follow-up
- All patients in both groups regained their pre-injury activity level; ankle scores and stress radiographs did not differ
- Reinjury was less frequent after surgery (1/15 vs 7/18; risk difference 32%)
- However Grade-II osteoarthritis was seen only in the surgical group (4/15 vs 0/18)
Arthroscopic vs Open Brostrom (Meta-analysis)
- 8 comparative studies, 408 patients (193 open, 215 arthroscopic)
- States that nearly 20% of acute sprains progress to chronic instability requiring surgery
- Arthroscopic repair gave modestly higher AOFAS scores and faster weightbearing (mean 9.0 vs 14.25 weeks)
- Complication rates, talar tilt and anterior drawer were comparable; open Brostrom-Gould remains the reference standard
Society Guidance on Ankle Sprain Care
- Use validated decision rules (Ottawa Ankle Rules) to limit unnecessary radiographs
- Functional rehabilitation with early weightbearing and proprioceptive training is first-line for acute sprains
- Reserve surgery for chronic mechanical instability that has failed structured rehabilitation
- Recommend bracing/taping plus neuromuscular training for athletes with recurrent sprains
Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Acute Ankle Sprain in Athlete
"25yo professional field-sport athlete, inversion injury 3 days ago. Swollen, positive anterior drawer. Previous sprains. Wants to play in the finals."
Chronic Instability Management
"28F, recurrent sprains x4/year. Fails physio. MRI shows ATFL tear. Normal alignment."
Examiner Challenge - Surgical Technique
"Describe your Brostrom-Gould technique. Where are the dangers? How do you set tension?"
MCQ Practice Points
Nerve Injury
Q: What is the most common complication of Brostrom repair? A: Superficial Peroneal Nerve (SPN) injury (neurapraxia or injury). It runs in the subcutaneous tissue superficial to the extensor retinaculum.
Ottawa Specifics
Q: Which malleolar zones require X-ray according to Ottawa rules? A: Posterior edge or tip of medial/lateral malleolus (distal 6cm). Tenderness anterior to the malleolus (ATFL site) does NOT mandate X-ray.
Varus Malalignment
Q: What is the primary cause of Brostrom failure? A: Unrecognized Hindfoot Varus. The deformity places constant strain on the repair. A calcaneal osteotomy may be required.
Ligament Injury Sequence
Q: In what order do the lateral ankle ligaments tear with increasing force? A: ATFL → CFL → PTFL. The ATFL is weakest (2mm thick, essentially capsular thickening) and tears first in plantarflexion. The CFL tears second in neutral/dorsiflexion. The PTFL only tears with complete dislocation (strongest ligament).
Chronic Instability Definition
Q: How do you differentiate mechanical vs functional ankle instability? A: Mechanical instability = objective laxity on examination (positive Anterior Drawer/Talar Tilt). Functional instability = subjective giving way without gross laxity (proprioceptive/neuromuscular deficit). Treatment differs: functional requires rehab; mechanical may need surgical reconstruction if rehab fails.
Guidelines, Registries & Global Practice
Global epidemiology. Lateral ankle sprain is the single most common musculoskeletal injury worldwide, with an estimated incidence of about 2-7 per 1000 person-years in the general population and far higher in court/jumping and field sports (basketball, volleyball, football/soccer). Around 40% present to emergency or primary care. Roughly 1 in 5 (about 20%) progress to chronic ankle instability with recurrent giving-way. There is no implant registry for soft-tissue ankle ligament surgery, so the evidence base is RCTs, cohorts and meta-analyses rather than national registries.
Side-by-Side Guideline Comparison
| Body / Region | Imaging | Acute Treatment | Surgery |
|---|---|---|---|
| Ottawa Rules (validated globally) | X-ray only if bony tenderness or unable to weight bear 4 steps | n/a | n/a |
| AAOS / US sports medicine | Selective radiographs; MRI for persistent pain | Functional rehab, early weightbearing, proprioception | Chronic mechanical instability after failed rehab |
| BOA / NICE (UK) | Ottawa Rules to limit X-rays | RICE then early functional rehab; brief support | Reserved for refractory chronic instability |
| ESSKA-AFAS / EFORT (Europe) | Stress US/MRI in chronic cases | Functional rehab; bracing for high-risk return | Anatomic repair (Brostrom-Gould) first-line |
High-Resource Settings
Ready access to MRI and ultrasound, supervised physiotherapy, suture-anchor and internal-brace constructs, and increasing use of arthroscopic Brostrom in specialist centres.
Limited-Resource Settings
Greater reliance on Ottawa Rules and clinical examination, functional rehabilitation with low-cost bracing/taping, and transosseous (drill-hole) Brostrom repair where suture anchors are unavailable. Outcomes of anatomic repair remain good without expensive implants.
Lateral Ankle Sprains Essentials
Clinical summary
Anatomy
- •ATFL: Weakest, injured first (Plantarflexion)
- •CFL: Stronger, injured second (Dorsiflexion)
- •SPN: Danger structure in approach
- •PTFL: Only tears with dislocation (strongest)
Assessment
- •Ottawa Rules: Posterior edge tenderness or inability to WB
- •Anterior Drawer: ATFL (greater than 3mm diff)
- •Talar Tilt: CFL (greater than 10 deg)
- •Always palpate proximal fibula (Maisonneuve)
Management
- •Acute: Functional Rehab (Brace, Move) superior to Cast
- •Chronic: Brostrom-Gould (Anatomic Repair)
- •Augmentation: Consider for Hyperlaxity/Heavy patients
- •Prophylactic bracing reduces re-injury by 50%
Complications
- •SPN Injury (Numbness)
- •Recurrence (Varus heel?)
- •Stiffness (Overtightening)
- •Missed OCL or peroneal pathology