How often does a sprained ankle damage cartilage?

After a second or third ankle sprain, the question most patients quietly ask — but rarely put to their clinician — is whether anything more serious has happened inside the joint. The short answer is: quite possibly yes.

Even after a single, straightforward sprain, osteochondral lesions (OCLs) — areas where cartilage and the bone beneath it have been bruised or damaged — are found in roughly 6–7% of cases. That figure is already higher than most people expect from what feels like a 'simple twist'. Once symptoms become severe or persistent, prevalence rises sharply, reaching 40–70% in patients attending specialist services with ongoing disability.

For those whose ankle has never quite recovered — developing the pattern of repeated 'giving way' known as chronic lateral ankle instability (CLAI) — the picture is clearer still. A 2022 meta-analysis pooling data from 2,145 patients found that approximately one in three ankles with established CLAI harbours a cartilage or osteochondral lesion, with a pooled rate of 32.2%.

The talus (the main ankle bone) bears the brunt in 85% of cases. Of those talar lesions, roughly two-thirds sit on the medial dome — the inner, deeper, more posteriorly located portion of the joint surface. This is the subtype least likely to repair itself, partly because it is less accessible to the body's own healing mechanisms.

Cartilage damage after ankle sprain, in other words, is not an unusual complication. In the context of recurrent instability, it is close to the expected trajectory.

Why each successive sprain causes deeper damage

The damage begins at the moment of the initial twist, before any pattern of instability has had time to establish itself. When the ankle inverts — rolling inward under load — the two main lateral ligaments, the anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL), take the brunt of the force. Simultaneously, the talar dome is compressed and sheared against the tibial surface. Lateral dome lesions arise specifically from the combination of inversion, dorsiflexion, and axial load; medial dome lesions from inversion combined with external rotation and plantarflexion. Either way, the cartilage and the bone immediately beneath it absorb an impact they were not designed to sustain.

If the ATFL and CFL do not heal fully — which occurs in up to 70% of first-time lateral sprains — the joint is left mechanically vulnerable. Each subsequent episode of 'giving way' subjects the talar dome to forces it can no longer distribute evenly. The cascade that follows is cumulative and sequential: abnormal kinematic loading drives trabecular microfractures in the subchondral bone; these trigger localised haemorrhage and inflammation, visible on MRI as bone marrow oedema (BME); the structural integrity of the subchondral plate progressively fails; and the overlying cartilage, deprived of its firm foundation, begins to soften, crack, and separate.

The joint does not reset between giving-way episodes. Each one deposits another increment of microtrauma onto an already compromised surface. In time, persistent microtrauma creates a locally ischaemic environment; where talar vascularity is disrupted — particularly in the watershed regions of the talar blood supply — localised cell death, or osteonecrosis, may develop, removing any remaining capacity for self-repair.

Untreated instability, in this sense, is not passive waiting. It is ongoing structural attrition.

When imaging is actually warranted

Knowing when to escalate from clinical assessment to imaging is, in practice, one of the most common points of uncertainty after an ankle sprain.

Plain X-ray is the correct first step — it excludes fracture and gross bony change — but it tells very little about cartilage. A normal X-ray does not rule out an osteochondral lesion; the majority of OCLs are invisible on plain film, and false reassurance at this stage is a genuine risk.

Three clinical triggers should prompt MRI:

• Symptoms persisting beyond six to eight weeks despite appropriate conservative management (rest, physiotherapy, structured loading)
• Mechanical symptoms at any point — catching, locking, or unprovoked giving-way — regardless of how recent the original sprain was
• A high-grade initial sprain: an audible pop at the moment of injury, rapid and significant swelling, or immediate inability to weight-bear

MRI at 1.5T is the gold standard for staging once an OCL is suspected. It characterises bone marrow oedema, lesion depth, and fragment stability — the three variables that most directly inform the decision between conservative management and intervention.

Where MRI spatial resolution is insufficient to assess the cartilage surface precisely, cone-beam CT (CBCT) arthrography adds the necessary detail. CT without contrast, rather than MRI, is preferred when the bony lesion dimensions need to be measured accurately for pre-operative planning.

A scan finding is one input into a clinical decision, not a diagnosis in itself. The same lesion visible on MRI may behave very differently depending on a patient's functional demands, symptom burden, and the degree of coexisting instability.

What lesion staging means for your treatment decision

Staging translates what MRI shows into a practical treatment decision. The critical threshold sits at Stage 2 — partial detachment of an osteochondral fragment, with evidence of a subchondral cyst or fissure beneath it. Below this threshold, conservative management is a reasonable first approach in most adults. At Stage 2 or above, surgical intervention is generally required.

Conservative management at earlier stages is not passive rest. It centres on structured physiotherapy targeting peroneal muscle strength and joint proprioception — the two deficits most directly linked to ongoing instability — alongside graduated load management. Injection support may be considered in parallel with rehabilitation where symptom burden justifies it.

Four factors sit alongside formal staging when the decision is made: lesion size, fragment stability, the extent of bone marrow oedema, and the patient's activity demands. A small, stable, oedema-free lesion in a less active individual is a materially different case from the same radiological stage in a competitive athlete.

Surgical stabilisation of the lateral ligaments — typically a Broström-type anatomic repair — can restore normal joint kinematics, but the evidence suggests it does not reliably reverse cartilage loss once it is established. The argument for early assessment rests on this asymmetry: the window in which the joint can be intercepted before loss becomes irreversible is finite, and its width varies between individuals.

Because no published data have established a validated sprain count or duration of instability at which a reversible lesion becomes permanent, what matters most when seeing a specialist is the full clinical picture: how many giving-way episodes, how long instability has been present, and which symptoms have changed over time. These are the details that allow an accurate individual judgement — and they are worth documenting before the appointment.

The link between ankle instability and joint arthritis

Arthritis rarely enters the thinking of a patient in their thirties or forties who has rolled their ankle twice. Yet the downstream risk from undertreated chronic instability is substantial — and it arrives measurably earlier than most people expect.

Up to 80% of all ankle osteoarthritis is post-traumatic in origin, and among people with established chronic ankle instability, published estimates suggest up to 78% eventually develop post-traumatic OA (PTOA). Even a single sprain, if it does not resolve fully, raises the lifetime risk of developing OA by approximately 46% — with women disproportionately affected at every stage of that progression.

The timeline is long but not benign. In the first twelve months after injury, chondrocyte death and pro-inflammatory cytokine release begin remodelling the joint environment. Between one and five years, chronic mechanical instability drives cartilage degradation. End-stage joint failure typically emerges ten to twenty years later — by which point the treatment options narrow considerably.

What makes this clinically significant is the age at which it arrives. Ankle PTOA patients are, on average, 14 years younger than people presenting with primary hip or knee OA. This is a working-age disease: the patient losing joint function is often still in employment, in sport, or raising a family.

Where an osteochondral lesion co-exists with chronic instability, the trajectory is worse still. The two conditions together accelerate whole-joint deterioration beyond what instability alone would produce. This is the argument for early specialist assessment: the window in which the joint can be intercepted before degeneration becomes structural is finite — and, critically, it is not the same for everyone.

Getting the right assessment before the window closes

Deciding to seek specialist input is simpler when the stakes are clear: cartilage loss, once established, does not reliably reverse. A specialist can determine — where a GP or physiotherapist alone cannot — whether the joint has already crossed that threshold, and what the most appropriate response is at the current stage.

Assessment typically combines a detailed history of previous sprains and functional instability with clinical examination of ligament laxity, proprioception, and signs of impingement or loose-body catching. Imaging is ordered where the clinical picture warrants it, with the modality matched to the question being asked.

The treatment pathway follows a staged logic: structured rehabilitation remains the foundation at earlier stages; injection support addresses symptom burden or, where an osteochondral defect has been confirmed at an appropriate stage, provides scaffold support for cartilage repair; surgical stabilisation is indicated for established lateral ligament failure; and joint preservation or replacement addresses end-stage disease.

For eligible osteochondral defects, one option within the injection support tier is ultrasound-guided ChondroFiller injection — an injectable collagen scaffold placed as an outpatient procedure. It addresses the cartilage defect specifically; the underlying ligament instability requires separate, parallel management. In the UK, ChondroFiller injection is delivered at the London Cartilage Clinic on Harley Street; assessments can be arranged at londoncartilage.com.

The throughline connecting all of the above is this: the window for intercepting cartilage damage before it becomes structural and permanent narrows with each giving-way episode. The stage at which specialist input is sought tends to define long-term outcome more than any single treatment choice.