Chronic Ankle Instability
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Direct answer
Chronic ankle instability is the story of sprains that keep recurring after an inversion injury — the anterior talofibular ligament, essentially always the first to fail, heals stretched or scarred and the ankle gives way on uneven ground. It divides into mechanical instability (measurable ligamentous laxity on drawer and tilt testing) and functional instability (proprioceptive and neuromuscular deficit with normal laxity), and most patients carry a blend of both. Structured rehabilitation with peroneal strengthening and balance training comes first for three to six months; the Brostrom anatomic repair, now increasingly arthroscopic, is the standard operation when rehab fails.
What you must remember
- Order of failure: anterior talofibular ligament (ATFL) injured in essentially every lateral sprain, calcaneofibular ligament (CFL) commonly involved in severe ones, posterior talofibular ligament rarely except in dislocation — the syndesmosis (high sprain) is a separate axis of injury.
- Functional versus mechanical: mechanical instability means demonstrable laxity — anterior drawer and talar tilt beyond the opposite side; functional instability means giving-way with normal ligamentous tension, driven by proprioceptive deficit, weakness and delayed peroneal reaction time.
- Test conventions: anterior drawer at 10-15 degrees of plantarflexion; absolute translation above about 10 mm or a side-to-side difference above 5 mm is conventionally positive, and talar tilt above 15 degrees or 10 degrees of difference — numbers worth quoting, with stress radiographs if needed.
- Rehabilitation first: three to six months of peroneal strengthening, proprioceptive work (wobble board, single-leg stance progression) and bracing; a substantial majority settle and never need surgery.
- Anatomic repair: Brostrom — imbrication and reefing of the attenuated ATFL (and CFL when involved); Brostrom-Gould adds the inferior extensor retinaculum as a reinforcement; arthroscopic versions give comparable results with less morbidity and allow addressing intra-articular pathology at the same sitting.
- Non-anatomic tenodeses (historic but examinable): Evans — peroneus brevis rerouted through a fibular tunnel; Chrisman-Snook — split peroneus brevis through talus, fibula and calcaneus; Watson-Jones — all stiffen the ankle at the cost of eversion power; now reserved for failed anatomic repairs with poor tissue.
- Reasons a repair fails: missed peroneal tendon tears, osteochondral lesions of the talus, unrecognised hindfoot varus (the cavus foot story) and syndesmotic laxity — examine for all before operating.
- Indian practice reality: cricket and kabaddi supply most of these ankles to teaching-hospital clinics; a crepe bandage is cheap but is not a rehabilitation programme — prescribing the wobble board is what separates the answer from the bandage.
From sprain to surgery
Walk the pathway the examiner expects. First inversion sprain: relative rest, ice, compression, early motion — and from the first week, balance work, because proprioception is injured along with the ligament. The patient returns twice more over eighteen months; each sprain is easier to provoke and the ankle feels "loose" on stairs. Examine standing and seated: hindfoot alignment (a subtle cavovarus changes the plan), peroneal strength against resistance, anterior drawer and talar tilt compared with the other side, and a syndesmosis squeeze. MRI is reserved for suspicion of peroneal tendon tear, osteochondral lesion or syndesmosis injury — the things that would divert the plan. With mechanically stable findings, twelve weeks of supervised proprioceptive training still fixes many chronic ankles; when laxity is demonstrable and giving-way persists despite that, Brostrom-Gould follows, with consent covering the small risk of stiffness and superficial peroneal nerve irritation.
The exam's favourite ligament
The ankle question is really about anatomy in motion: inversion in plantarflexion loads the ATFL, inversion in dorsiflexion loads the CFL, which is why the "just ATFL" answer for every sprain is wrong in severe injuries and why the drawer test is performed in plantarflexion. Students lose marks by saying "lateral ligament complex" when the examiner wants the named ligament and the position that stresses it. The second favourite distinction — functional versus mechanical instability — is asked as a definition, and the trap is treating them as mutually exclusive; a single chronic ankle commonly has measurable laxity plus a proprioceptive deficit, and surgery only fixes one half of that pair, which is why rehabilitation never stops after a Brostrom.
Frequently asked questions
Which ligament is injured first in an inversion ankle sprain?
The anterior talofibular ligament, stressed by inversion in plantarflexion; the calcaneofibular ligament joins it in more severe injuries.
How is mechanical instability demonstrated clinically?
An increased anterior drawer at 10-15 degrees of plantarflexion and talar tilt compared with the opposite side — on testing or stress radiographs.
What does the Gould modification add to the Brostrom repair?
Advancement of the inferior extensor retinaculum over the repaired ATFL, reinforcing the reconstruction and controlling subtalar tilt.
Why prefer anatomic repair over tenodesis procedures?
Anatomic repairs restore normal ligament anatomy with 85-90 percent good results, while Evans-type tenodeses sacrifice the peroneus brevis, stiffen the ankle and weaken eversion.
Name two reasons a Brostrom repair might fail.
Missed peroneal tendon tear or osteochondral talar lesion left untreated; uncorrected hindfoot varus that keeps overloading the repair.