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1 · SNAPSHOT

Chronic Ankle Instability body chart — Illustrative, not diagnostic. Canva body chart for Chronic Ankle Instability.

Who: Anyone who sprained an ankle and never fully got over it. Court and field sports especially.
What: Recurrent giving way, recurrent sprains, and a persistent sense that the ankle cannot be trusted.
How it behaves: Uneven ground, fatigue, changes of direction. Often "it just goes" with no warning.

The one thing to take from this page:

This condition is defined by what the patient reports. Not by laxity, and not by your hands.

The International Ankle Consortium criteria [1]:


1	At least one significant ankle sprain — inflammatory symptoms, at least one day of interrupted activity — at least 12 months ago
2	At least two episodes of giving way in the previous 6 months, and/or recurrent sprain, and/or feelings of instability
3	Confirmation on a validated patient-reported instrument — CAIT under 24, and/or IdFAI 11 or more

Not one of those three is a physical test.

How common, honestly: the published figures span 10% to 70%, and no prospective study reporting a confidence interval was found. The two most defensible numbers: 46% (range 9–76%) among people with a history of ankle sprain across 9 studies and 3,804 participants; and 131 of 362 (36.2%) developing CAI at a mean of 3.0 years after a first sprain.

The spread is the finding. (And "up to 40%" — the figure everyone quotes — traces to an unsourced estimate in one 2019 paper's abstract. Don't quote it.)

⚠️ No Australian guideline exists for chronic ankle instability. Anchored to the JOSPT Ankle Stability and Movement Coordination Impairments CPG [2], whose ICF category is this pattern. The definitional scaffolding, though, was substantially built in Sydney and Brisbane — and the CAIT is a University of Sydney instrument.

Pattern > Label. Continues directly from the lateral ankle sprain page, which flagged three claims it could not support. This page settles them.

2 · SE — THE SUBJECTIVE PATTERN (the 70%)

Five stages, in your course's order — and here the subjective essentially IS the diagnosis.

MAIN PROBLEM

"It keeps going." "I don't trust it on uneven ground." "I've done it four times now."

BODY CHART

Often diffuse, often lateral, frequently not the main complaint at all — the instability is.
Persistent focal pain deep in the joint, catching or locking → osteochondral lesion. §4.
Posterolateral, behind the fibula, with a snap → peroneal tendons. §3.

HISTORY — and this is the case definition

Work through the three IAC criteria explicitly, because they are the diagnosis:

The index sprain. When, how bad, did it stop them for at least a day, and was it more than 12 months ago?
Giving way. How many times in the last six months? Doing what? Two or more is the threshold.
Previous management. Was it treated at all? (This matters — the one home-programme trial that reduced recurrence found the benefit confined to athletes whose original sprain was NOT medically treated.)

BEHAVIOUR

Aggs: uneven ground, court sports, changes of direction, fatigue, sand, stairs in the dark.
Eases: flat predictable surfaces, taping or bracing, boots.
Do they avoid things? Perceived instability without avoidance is a different problem from perceived instability with it.
Irritability: if pain is a feature at all, use the three-part definition. Often it is not.

SPECIAL / SCREENING QUESTIONS

Locking, catching, deep joint pain, swelling that persists, numbness, and — in an adolescent with recurrent sprains — a family history of foot problems. See §4.

The thing to hand them

Use the CAIT. It is Australian, it is free, and its numbers are better than the manual test you were going to reach for:


Validation threshold	27.5 (Youden index 68.1)
Sensitivity / specificity at that threshold	82.9% / 74.7%
Test–retest ICC	0.96
Cronbach's α	0.83
The research cut-off used by the IAC	under 24 — deliberately more conservative

([3], 236 community volunteers, University of Sydney.)

Know both numbers and know why they differ — 27.5 is the instrument's own optimum, 24 is the stricter line drawn for research enrolment. An educator will ask.

Two episodes in six months and a CAIT under 24 is a diagnosis. A positive anterior drawer is not.

Assessing this region? Download the Ankle & Foot assessment template →

3 · HYPOTHESIS RANKING

Competing pattern	The one discriminating feature
Osteochondral lesion of the talus	Deep joint pain, catching, persistent swelling. Pain out of proportion to the instability — §4
Peroneal tendinopathy or subluxation	Posterolateral, behind the fibula, and pain on resisted dorsiflexion and eversion. A snap on rotation
Missed syndesmotic injury	High, above the joint line. Pain on external rotation. Often missed at the index sprain
Occult fracture	Focal bone tenderness. Ottawa rules applied at the index event, if they were
Tarsal coalition	Adolescent, recurrent sprains, a stiff subtalar joint. Image bilaterally
Coper	Sprained once, fully recovered, no giving way. Not a diagnosis — a comparison group

The model that failed — this is the page

You were taught a binary: mechanical instability versus functional instability. It does not survive.

In 137 ankles tested for model fit and 81 CAI ankles for impairment ([4], University of Sydney):


Fitted the mechanical + functional model	only 56.5% (n = 61)
Fitted a model of three independent or overlapping components	100% (n = 108)
Perceived instability ALONE — no mechanical component at all	42.6%
Recurrent sprain + perceived instability	30.5%
Remaining combinations	26.9%

The binary fails to classify 43.5% of ankles. And the single largest group — nearly half — has no mechanical component whatsoever, which means the laxity tests you were taught examine something that is absent in the biggest subgroup.

The current model is four domains: pathomechanical, sensory-perceptual, motor-behavioural, plus personal and environmental factors, under a biopsychosocial frame [5].

And a related myth, while you are here: more torn ligaments does not mean more instability. Across 9 papers with imaging-confirmed ligament counts and ≥12 months follow-up, combined ATFL + CFL rupture showed no significant correlation with progression to CAI versus isolated ATFL rupture — though it did associate with worse outcome scores and less return to full sport [6].

Jones' hypothesis categories that change your plan: patient perspectives — perceived instability is the largest subgroup — plus impairments, sources of symptoms and contributing factors.

Nearly half of these ankles are not loose. They are unconvincing to their owner, which is a different problem needing a different programme.

4 · RED FLAGS — DON'T MISS THIS

This section is free, on every pattern, forever.

The flags here are not systemic. They are the things hiding inside a recurrent sprain — and they are common.

Signs / symptoms	Implication
Deep joint pain, catching, locking, persistent swelling	Osteochondral lesion of the talus
Posterolateral pain, snapping behind the fibula, pain on resisted dorsiflexion and eversion	Peroneal tendon tear or subluxation
High pain above the joint line, pain on external rotation	Missed syndesmotic injury
Focal bone tenderness, unable to weight-bear at the time	Occult fracture
Adolescent, recurrent sprains, stiff or painful subtalar joint	Tarsal coalition — image bilaterally
Numbness, burning, night symptoms	Nerve involvement

What is actually in there — the imaging that should change your index of suspicion

MRI within 10 days of acute ligamentous ankle injury, 171 injuries [7]:


Lateral ligament injury	73%
Anterior syndesmosis injury	38%
Cartilage or osteochondral lesion	14% — 85% of those cartilage rather than osteochondral

More than a third of "lateral ankle sprains" involve the syndesmosis. That is the injury most likely to have been missed at the index event, and the most likely reason a recurrent sprainer is not responding.

And what predicts the ankle that will not settle

In 362 first-episode sprains, all imaged with radiograph and MRI within two weeks, followed a mean of 3.0 years [8] — 131 of 362 (36.2%) developed CAI, with these independent predictors:


Large bone marrow lesion of the talus	OR 2.69 (95% CI 1.30–5.58), p = 0.008
Grade 2 tibiotalar effusion	OR 2.61 (1.39–4.89), p = 0.003
Posterior talofibular ligament injury	OR 2.17 (1.05–4.48), p = 0.035
BMI	OR 1.09 (1.02–1.17)
Younger age	OR 0.96 (0.93–1.00)

(Carry the caveat: retrospective, single centre, and every patient was imaged — selection toward more severe injury.)

A recurrent sprainer with deep joint pain, catching, or swelling that will not settle has something in the joint until imaging says otherwise.
More than a third of lateral ankle sprains involve the syndesmosis. Ask about the high one.
An adolescent with repeated sprains and a stiff subtalar joint gets bilateral imaging.

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Twelve slides on this pattern: what you'll hear, what to examine, what to do. Free with an account.

Guideline anchor

No Australian guideline for this presentation.

Anchored to Ankle Stability and Movement Coordination Impairments: Lateral Ankle Ligament Sprains Revision 2021 — JOSPT clinical practice guideline (Martin et al.)

PubMed

No Australian clinical guideline or clinical care standard exists for chronic ankle instability. But the definitional scaffolding was substantially built in Sydney and Brisbane — Refshauge and Hiller (University of Sydney) and Vicenzino (University of Queensland) are named authors on the 2014 criteria, the 2016 consensus and the 2018 ROAST, and the CAIT is a University of Sydney instrument.

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The evidence summary is for members

Verified diagnostic accuracy, where the evidence stands and what it doesn't settle. Free with an account.

Sources · 24

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Every source on this page resolves and title-verifies against PubMed. Newest first.

2014Gribble et al. (2014). Selection criteria for patients with chronic ankle instability in controlled research: a position statement of the International Ankle Consortium. British journal of sports medicine, 48(13), 1014-8. https://doi.org/10.1136/bjsports-2013-093175
2021Martin et al. (2021). Ankle Stability and Movement Coordination Impairments: Lateral Ankle Ligament Sprains Revision 2021. The Journal of orthopaedic and sports physical therapy, 51(4), CPG1-CPG80. https://doi.org/10.2519/jospt.2021.0302
2006Hiller et al. (2006). The Cumberland ankle instability tool: a report of validity and reliability testing. Archives of physical medicine and rehabilitation, 87(9), 1235-41. https://doi.org/10.1016/j.apmr.2006.05.022
2011Hiller et al. (2011). Chronic ankle instability: evolution of the model. Journal of athletic training, 46(2), 133-41. https://doi.org/10.4085/1062-6050-46.2.133
2019Hertel & Corbett (2019). An Updated Model of Chronic Ankle Instability. Journal of athletic training, 54(6), 572-588. https://doi.org/10.4085/1062-6050-344-18
2021Pacheco et al. (2021). Chronic ankle instability has no correlation with the number of ruptured ligaments in severe anterolateral sprain: a systematic review and meta-analysis. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA, 29(11), 3512-3524. https://doi.org/10.1007/s00167-021-06610-y
2025Baltes et al. (2025). The Prevalence, Size, and Anatomic Location of Cartilage and Osteochondral Lesions in Athletes With an Acute Ligamentous Ankle Injury. The American journal of sports medicine, 53(9), 2173-2180. https://doi.org/10.1177/03635465251344187
2023Zhang et al. (2023). Risk factors for chronic ankle instability after first episode of lateral ankle sprain: A retrospective analysis of 362 cases. Journal of sport and health science, 12(5), 606-612. https://doi.org/10.1016/j.jshs.2023.03.005
2013Croy et al. (2013). Anterior talocrural joint laxity: diagnostic accuracy of the anterior drawer test of the ankle. The Journal of orthopaedic and sports physical therapy, 43(12), 911-9. https://doi.org/10.2519/jospt.2013.4679
2017Davda et al. (2017). Peroneal tendon disorders. EFORT open reviews, 2(6), 281-292. https://doi.org/10.1302/2058-5241.2.160047
2017Doherty et al. (2017). Treatment and prevention of acute and recurrent ankle sprain: an overview of systematic reviews with meta-analysis. British journal of sports medicine, 51(2), 113-125. https://doi.org/10.1136/bjsports-2016-096178
2011McGuine et al. (2011). The effect of lace-up ankle braces on injury rates in high school basketball players. The American journal of sports medicine, 39(9), 1840-8. https://doi.org/10.1177/0363546511406242
2012McGuine et al. (2012). The effect of lace-up ankle braces on injury rates in high school football players. The American journal of sports medicine, 40(1), 49-57. https://doi.org/10.1177/0363546511422332
2025Yang et al. (2025). What Will Deliver the Best Bang-For-Your-Treatment-Buck? Treatment Effects of Physical Therapy Approaches to Managing Chronic Ankle Instability: A Network Meta-Analysis of Randomized Controlled Trials. The Journal of orthopaedic and sports physical therapy, 55(1), 26-44. https://doi.org/10.2519/jospt.2024.12601
2023Koshino & Kobayashi (2023). Effects of Conservative Interventions on Static and Dynamic Balance in Individuals With Chronic Ankle Instability: A Systematic Review and Meta-analysis. Archives of physical medicine and rehabilitation, 104(4), 673-685. https://doi.org/10.1016/j.apmr.2022.10.014
2021Luan et al. (2021). Does Strength Training for Chronic Ankle Instability Improve Balance and Patient-Reported Outcomes and by Clinically Detectable Amounts? A Systematic Review and Meta-Analysis. Physical therapy, 101(7). https://doi.org/10.1093/ptj/pzab046
2022Han et al. (2022). Can Therapeutic Exercises Improve Proprioception in Chronic Ankle Instability? A Systematic Review and Network Meta-analysis. Archives of physical medicine and rehabilitation, 103(11), 2232-2244. https://doi.org/10.1016/j.apmr.2022.04.007
2022Picot et al. (2022). Which Functional Tests and Self-Reported Questionnaires Can Help Clinicians Make Valid Return to Sport Decisions in Patients With Chronic Ankle Instability? A Narrative Review and Expert Opinion. Frontiers in sports and active living, 4, 902886. https://doi.org/10.3389/fspor.2022.902886
2018Delahunt et al. (2018). Clinical assessment of acute lateral ankle sprain injuries (ROAST): 2019 consensus statement and recommendations of the International Ankle Consortium. British journal of sports medicine, 52(20), 1304-1310. https://doi.org/10.1136/bjsports-2017-098885
2016Gribble et al. (2016). 2016 consensus statement of the International Ankle Consortium: prevalence, impact and long-term consequences of lateral ankle sprains. British journal of sports medicine, 50(24), 1493-1495. https://doi.org/10.1136/bjsports-2016-096188
2016Gribble et al. (2016). Evidence review for the 2016 International Ankle Consortium consensus statement on the prevalence, impact and long-term consequences of lateral ankle sprains. British journal of sports medicine, 50(24), 1496-1505. https://doi.org/10.1136/bjsports-2016-096189
2021Lin et al. (2021). The epidemiology of chronic ankle instability with perceived ankle instability- a systematic review. Journal of foot and ankle research, 14(1), 41. https://doi.org/10.1186/s13047-021-00480-w
2021Mollà-Casanova et al. (2021). Effects of balance training on functionality, ankle instability, and dynamic balance outcomes in people with chronic ankle instability: Systematic review and meta-analysis. Clinical rehabilitation, 35(12), 1694-1709. https://doi.org/10.1177/02692155211022009
2019Delahunt & Remus (2019). Risk Factors for Lateral Ankle Sprains and Chronic Ankle Instability. Journal of athletic training, 54(6), 611-616. https://doi.org/10.4085/1062-6050-44-18

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