More damage than the X-ray shows

A successfully repaired ankle fracture should, in theory, mean the problem is solved. Yet a significant number of patients find themselves still struggling with pain, stiffness, or swelling months after the metalwork goes in — and the explanation often lies not in the fracture itself, but in cartilage damage that never appeared on the pre-operative scans.

When surgeons perform arthroscopy at the same time as ankle fracture fixation, the findings are striking: chondral lesions are present in approximately 78% of cases, and 43% of those involve Grade IV full-thickness injuries to the talar dome — the most severe category of cartilage loss. The critical detail is that the vast majority of these lesions are invisible on standard X-rays and are frequently missed on CT imaging as well. Even in ankle injuries without any fracture at all, 3T MRI detects osteochondral lesions in around 14% of cases — structural damage caused by the force of the injury alone, without a single bone breaking. This systematic gap between what standard imaging shows and what is actually present inside the joint goes a long way towards explaining why ankle cartilage damage is so consistently under-recognised and under-managed. It also explains a population-level pattern that surprises many patients: most ankle osteoarthritis is not the result of age-related wear and tear, but of earlier trauma — a fracture, a severe sprain, or the cumulative effect of joint disruption that was never fully addressed at the time.

Understanding why the injury causes this degree of hidden damage requires looking at what happens inside the joint in the hours and days after a fracture.

Why the whole joint is at risk, not just the fracture site

The moment a bone breaks inside the ankle joint, blood and inflammatory fluid mix instantly within the joint cavity — a phenomenon researchers call the synovial fluid fracture hematoma, or SFFH. Unlike a bruise in soft tissue, this hematoma has nowhere to drain: it sits in direct contact with every cartilage surface in the joint, not just the area around the fracture line. That distinction matters enormously.

The fluid is loaded with inflammatory signalling molecules called cytokines and with enzymes known as matrix metalloproteinases (MMPs), which break down the structural proteins that give cartilage its load-bearing properties. Laboratory studies exposing cartilage tissue to ankle SFFH show that chondrocyte viability — the survival of the cells responsible for maintaining cartilage — falls by approximately 34% within just three days of exposure. At the same time, the genes that drive healthy cartilage upkeep, COL2A1 (which codes for the correct form of structural collagen) and SOX9 (a master regulator of cartilage cell identity), are significantly downregulated. In their place, the tissue begins depositing disorganised collagen I — the type of collagen found in scar tissue rather than functional articular cartilage.

This means the biochemical environment created by the fracture is itself a driver of joint deterioration, independent of whatever mechanical damage occurred at the break site. It is now understood as a primary pathway towards post-traumatic osteoarthritis.

Early-stage laboratory research suggests this cascade may be partially suppressible: adding agents such as IL-1 receptor antagonist (IL-1Ra) or the antibiotic doxycycline to SFFH-exposed cartilage reduced some of the damage in vitro. Clinical evidence in living patients does not yet exist, but the finding points to a biologically plausible rationale for intervening quickly after ankle fracture — a window that current standard care does not yet systematically address.

Who is most likely to develop arthritis after an ankle fracture

Several patient characteristics substantially shift the odds of progression to arthritis after ankle fracture. The following are each supported by outcome data:

• Age. Patients over 30 are significantly more likely to sustain Grade IV talar dome lesions at the time of fracture. Age ≥60 is also an independent risk factor for radiographic post-traumatic osteoarthritis (PTOA) at minimum three-year follow-up.
• BMI ≥28 kg/m². Higher body mass increases mechanical load through an already-damaged joint surface.
• Heavy physical labour. Occupational loading beyond moderate intensity is independently associated with PTOA progression.
• Posterior malleolus involvement. Fractures affecting more than 25% of the posterior articular surface carry a significantly worse joint prognosis.
• Articular incongruency. Even a small residual step in the joint surface after fixation markedly accelerates cartilage wear over subsequent years.
• Clinical frailty. In elderly patients with trimalleolar fractures, a Clinical Frailty Scale score of 5–9 carries an odds ratio of approximately 9 for developing PTOA — a greater single-factor risk than any of the mechanical variables above.

Patients carrying two or more of these features — for example, a 65-year-old with a BMI of 30, posterior malleolus involvement, and a physically demanding job — have a meaningfully compressed timeline to symptomatic arthritis. For this group, earlier specialist review is worth pursuing rather than standard fracture clinic follow-up alone.

How ankle cartilage damage is assessed

Three imaging tools are typically used in sequence, each revealing what the last cannot.

Plain X-rays are the starting point at every ankle fracture. They define the fracture pattern and overall joint alignment, but they image bone rather than cartilage. The majority of chondral lesions are invisible on plain films, which is why a reassuring post-operative X-ray does not rule out significant cartilage injury — it simply means the bone looks acceptable.

CT scanning adds bony and subchondral detail that plain films cannot match: the three-dimensional shape of an osteochondral defect, the integrity of the subchondral plate, and loose bony fragments are all better characterised on CT, making it the preferred tool for pre-operative bony planning. Its limitation is that purely cartilaginous lesions — those without an associated bone change — remain invisible on CT as they do on X-ray.

3T MRI is the current clinical standard for assessing cartilage itself. It identifies osteochondral lesions in 14% of acute ankle injuries and is sensitive to bone marrow oedema, haemorrhage, and subchondral changes that accompany early damage. Advanced T2 relaxation time mapping goes a step further: by measuring extracellular matrix changes rather than visible structural defects alone, it can detect biochemical deterioration within days of injury, before any discrete lesion has formed. The features that carry the greatest prognostic weight on MRI are lesion depth, the presence of subchondral cysts, and the extent of bone marrow oedema surrounding the lesion.

Arthroscopy remains the gold standard not because imaging has failed but because direct visualisation resolves ambiguity that no scan can, and — critically — allows simultaneous treatment in the same procedure. Where imaging findings raise questions that will change clinical management, arthroscopy provides the definitive answer.

A normal X-ray, in short, opens the investigation for a patient with persistent post-fracture symptoms rather than closing it.

The treatment pathway from conservative care to intervention

For most patients, management begins conservatively — and for roughly half, that is where it ends.

Stage one: conservative care

Small, stable, non-displaced lesions under 1 cm with no mechanical symptoms (locking, catching, or giving way) are managed initially with a six-week non-weight-bearing period in a boot, followed by physiotherapy and a graduated return to load. Intra-articular injections of hyaluronic acid (HA) or platelet-rich plasma (PRP) can support symptom control and joint environment during this phase. Published data suggest conservative care succeeds in 45–59% of adults, making a genuine trial of at least three months appropriate before escalation is considered.

The decision thresholds for intervention

Surgery moves from an option to a recommendation when: a fragment is displaced or loose within the joint; the defect exceeds approximately 1–1.5 cm²; or symptoms persist beyond three to six months of structured conservative management despite an adequate rehabilitation programme.

The regenerative injection option

For lesions that have not settled with conservative care but do not yet meet the size or displacement thresholds for operative repair, injectable collagen scaffold treatment — such as the ChondroFiller injection, available as an ultrasound-guided outpatient procedure — offers a regenerative intermediate step. The scaffold gels within the defect and is intended to recruit the patient's own progenitor cells to support new cartilage matrix formation. This distinguishes it mechanistically from HA or PRP, which modulate the joint environment without providing structural scaffold. The comparative evidence base for injectable scaffold versus surgical repair in this size range is still maturing, and individual suitability requires specialist assessment.

Operative cartilage repair

Where surgical intervention is indicated, the choice of technique tracks lesion size. Arthroscopic bone marrow stimulation — microfracture or drilling — is the standard approach for defects under 1.5 cm². Larger or more complex lesions, or those that have failed marrow stimulation, may be addressed with autologous matrix-induced chondrogenesis (AMIC), autologous chondrocyte implantation (ACI), or osteochondral grafting; these are theatre-based procedures with longer rehabilitation demands.

Not every patient progresses through every stage. A 35-year-old with a 0.8 cm stable medial talar lesion and mild symptoms may remain well-managed conservatively for years; a 60-year-old with posterior malleolus involvement and a loose fragment may need intervention within weeks of fracture fixation.

When to seek a specialist assessment

Persistent ankle pain, stiffness, or swelling three or more months after fracture fixation — even when the fracture surgeon's follow-up X-ray looked acceptable — is reason enough to seek a cartilage-focused specialist assessment rather than continuing to wait. The imaging that confirmed bony union does not speak to cartilage, and by three months the acute inflammatory window described earlier has already run its course. Patients carrying one or more of the higher-risk features covered in section three — age over 30, BMI at or above 28 kg/m², posterior malleolus involvement, or occupationally heavy physical load — have cause to seek review before symptoms worsen, rather than after they do.

A specialist cartilage assessment is typically straightforward in structure: a detailed clinical history, examination of ankle range of motion and stability, and a review of existing imaging. Where a 3T MRI has not yet been arranged, this is usually the first practical step. From that foundation, the clinician can discuss lesion grade, individual risk profile, and the realistic range of options — from continuing conservative care, through injectable scaffold treatment such as the ChondroFiller injection (available as an ultrasound-guided outpatient procedure at the London Cartilage Clinic on Harley Street, without general anaesthetic), to a referral pathway towards operative repair where defect size or clinical picture warrants it.

The practical argument for not deferring that conversation is straightforward: the evidence that cartilage injury is both more prevalent and more biochemically active than plain radiographs reveal means that earlier assessment preserves options rather than removing them. Arriving at a specialist review before a lesion has progressed to end-stage change is precisely when the full range of regenerative and restorative approaches remains genuinely available.

1. [1] Ankle Arthroscopy for Diagnosis and Treatment of Full Thickness Cartilage Lesions in the Setting of Ankle Fracture. (2017). https://doi.org/10.1177/2473011417S000233 https://doi.org/10.1177/2473011417S000233
2. [2] The Prevalence, Size, and Anatomic Location of Cartilage and Osteochondral Lesions in Athletes With an Acute Ligamentous Ankle Injury. (2025). https://doi.org/10.1177/03635465251344187 https://doi.org/10.1177/03635465251344187
3. [3] Intra-Articular Synovial Fluid With Hematoma After Ankle Fracture Promotes Cartilage Damage In Vitro Partially Attenuated by Anti-Inflammatory Agents. (2021). https://doi.org/10.1177/10711007211046952 https://doi.org/10.1177/10711007211046952
4. [4] Post-traumatic osteoarthritis after ankle fracture fixation: A minimum three-year follow-up.. (2025). https://doi.org/10.1016/j.fas.2025.02.014 https://doi.org/10.1016/j.fas.2025.02.014
5. [5] Exposure of Tissue-Engineered Cartilage Analogs to Synovial Fluid Hematoma After Ankle Fracture Is Associated With Chondrocyte Death and Altered Cartilage Maintenance Gene Expression. (2023). https://doi.org/10.1177/10711007231178829 https://doi.org/10.1177/10711007231178829
6. [6] Potential Roles of Inflammation on Post-Traumatic Osteoarthritis of the Ankle. (2024). https://doi.org/10.3390/ijms25115903 https://doi.org/10.3390/ijms25115903
7. [7] Mechanistic Parallels Between Early Post-Fracture and Post-Traumatic Ankle Osteoarthritis: Identifying Synovial Targets for Prevention and Treatment. (2025). https://doi.org/10.1177/2473011425s00323 https://doi.org/10.1177/2473011425s00323
8. [8] Etiology, Classification, Diagnostics, and Conservative Management of Osteochondral Lesions of the Talus. 2023 Recommendations of the Working Group 'Clinical Tissue Regeneration' of the German Society of Orthopedics and Traumatology. (2023). https://doi.org/10.1177/19476035231161806 https://doi.org/10.1177/19476035231161806
9. [9] Subchondral bone conditions influence pain in patients with osteochondral lesion of the talus. (2025). https://doi.org/10.1007/s00402-025-05956-z https://doi.org/10.1007/s00402-025-05956-z
10. [10] Osteochondral Lesion of the Talus Dome: What's New in the Therapeutic Protocol. (2023). https://doi.org/10.36347/sjmcr.2023.v11i06.029 https://doi.org/10.36347/sjmcr.2023.v11i06.029
11. [11] The clinical frailty scale is associated with an increased risk of postoperative complications and the development of post-traumatic osteoarthritis in elderly patients with trimalleolar ankle fractures. (2025). https://doi.org/10.1186/s13018-025-05499-4 https://doi.org/10.1186/s13018-025-05499-4
12. [12] Results of the AMIC® method in patients operated on for an osteochondral lesion of the talar dome (OLTD) at a mean follow-up of 34 months.. (2024). https://doi.org/10.1016/j.otsr.2024.104020 https://doi.org/10.1016/j.otsr.2024.104020