The short answer: three injections, three very different timelines

The answer depends on what each injection is designed to do — and the timelines differ markedly.

Corticosteroid injections work within 2–7 days but typically provide pain relief for around 6–12 weeks. NHS guidance cites approximately two months as the usual duration; a minority of patients see benefit lasting up to six months. Frequency is capped at three to four injections per year in the same joint to avoid accelerating cartilage damage.

Hyaluronic acid (HA) viscosupplementation works more slowly but lasts considerably longer. A 2024 cross-sectional study of 105 patients (149 knees) found a mean duration of effectiveness of 48.2 ± 24.8 weeks — roughly 11 months — while extended-release single-injection formulations averaged around 52 weeks even in moderate-to-advanced osteoarthritis. Upper-end estimates reach 12–18 months in milder disease.

ChondroFiller™ sits in a different category altogether. Rather than delivering a temporary depot of pain-relieving or lubricating agent, this injectable collagen scaffold promotes the body's own repair processes through matrix-induced chondrogenesis. Published follow-up from the Jerosch et al. PMCF study shows IKDC scores rising from 47.6 before treatment to approximately 80 at 36 months, with improvement sustained — not declining — at the three-year mark. The goal is structural repair of the defect itself, not symptom masking.

For patients with focal cartilage defects (up to 6 cm²), the question of 'how long does it last' therefore needs reframing: with corticosteroids and HA, relief eventually wears off; with ChondroFiller, the aim is to address the underlying defect. Patient selection and defect type matter as much as the duration figures themselves.

Why corticosteroids fade after 6–12 weeks

Corticosteroids work by suppressing the inflammatory cascade — blocking the prostaglandins and cytokines responsible for pain and swelling. The mechanism is fast and, in the short term, often substantial: onset typically occurs within two to seven days. But this is precisely where the mechanism's strength becomes its limitation. Once the anti-inflammatory effect clears, the underlying joint structure is exactly as it was — or worse.

The 6–12 week duration reflects this directly. Corticosteroids do not stimulate tissue repair, halt cartilage breakdown, or alter the biological environment of the joint in any lasting way. When the drug effect dissipates, symptoms return and the degenerative process continues unchanged.

The safety constraint on repeat use is not arbitrary. Frequency is limited to three to four injections per year in the same joint because the evidence points to a structural cost of repeated dosing. McAlindon and colleagues' 2017 JAMA randomised controlled trial found measurable cartilage volume loss in patients receiving repeated intra-articular triamcinolone compared with saline controls — raising the concern that the corticosteroid may accelerate the very deterioration it is being used to manage.

None of this renders the injection without value. It remains appropriate for an acute inflammatory flare, as a short-term bridge before a more targeted procedure, or as a diagnostic injection to confirm the source of pain. The difficulty arises when a short-term tool is asked to carry a long-term management burden — which, in progressive or structural joint disease, it cannot.

Hyaluronic acid: symptom control for roughly 11 months

Unlike a drug that acts on the inflammatory cascade, hyaluronic acid works by supplementing the viscoelastic properties of synovial fluid — restoring some of the cushioning and lubrication that the osteoarthritic joint has lost. No structural change occurs in the cartilage itself; when the effect wanes, the joint returns to its pre-injection state.

The duration figures introduced above come from reasonably robust prospective data, but individual variation is wide. The 2024 cross-sectional study (105 patients, 149 knees) recorded a standard deviation of ±24.8 weeks alongside its 48.2-week mean — meaning a substantial proportion of patients experienced relief well outside that average in either direction. Clinical predictors of a shorter response include a BMI above 27.5 kg/m², involvement of more than one compartment, a sedentary lifestyle, and having completed more than three prior courses of viscosupplementation. Patients with milder radiographic disease (Kellgren–Lawrence grade 1–2) averaged 62.6 weeks compared with 48.9 weeks in grade 3–4 knees, suggesting that earlier intervention may prolong benefit.

Guideline bodies diverge on HA: OARSI offers conditional support; the AAOS and ACR are more sceptical, reflecting the heterogeneous preparation methods and patient populations across the published trials. What the evidence does consistently show is that HA provides better medium-term symptom control than corticosteroids at the 26-week mark in mild-to-moderate knee osteoarthritis — a meaningful advantage over the short-term tier, even if it remains firmly within the palliative category rather than the regenerative one.

ChondroFiller: scaffold repair, not a depot that wears off

Categorically, ChondroFiller™ belongs to a different class of intervention from either of the options discussed above. Delivered as an ultrasound-guided outpatient injectable, the treatment places a CE-marked Type I collagen gel directly into a focal cartilage defect — but the collagen itself is not the therapeutic endpoint. Its role is to act as a three-dimensional scaffold that recruits the patient's own progenitor cells from the surrounding synovium and subchondral bone, enabling a process known as acellular matrix-induced chondrogenesis. Over six to twenty-four months, those cells colonise the matrix and lay down hyaline-like repair tissue, progressively filling the defect from within.

Because the intended outcome is structural rather than symptomatic, the question of 'how long does it last?' does not map cleanly onto a corticosteroid or HA framework. There is no drug depot to metabolise, no lubricant to dilute. If the repair process completes successfully, the structural change persists — making the durability profile fundamentally different in character, not merely in degree.

The published clinical evidence is the most direct argument for this distinction. The Jerosch et al. post-market clinical follow-up study shows mean IKDC scores rising from 47.6 before treatment to 67.3 at twelve months and to approximately 80 at thirty-six months. Critically, the score did not plateau and begin to fall between year one and year three — it continued to improve, the opposite trajectory from a temporary treatment clearing the system. Structural MRI data in European knee studies corroborate this: MOCART scores reached 81.6 to 84.3 at one year, consistent with more than 80% defect filling and good integration into the surrounding native cartilage, rising from 65.3 at the four-week stage as the scaffold matured.

The thirty-six-month follow-up represents the current ceiling of published knee data, and claims beyond that horizon remain aspirational rather than evidence-based. What the available evidence does establish is a trajectory of sustained structural gain — a profile the two palliative tiers cannot replicate.

These treatments suit different patients — and that changes the comparison

ChondroFiller™ carries a specific structural indication: focal cartilage defects up to 6 cm² in a joint without diffuse osteoarthritis. Corticosteroids and HA address a fundamentally broader picture — symptomatic osteoarthritis across one or more joint compartments, where the cartilage loss is widespread rather than localised. These are not competing solutions for the same clinical problem, and that distinction matters more than any duration figure when a patient is deciding which pathway applies to them.

The Tönnis grading system provides the clearest line. In the published hip cohort study (12–60 months follow-up), patients with pre-existing Tönnis grade 2–3 osteoarthritis — indicating moderate-to-severe joint degeneration — had poor outcomes with ChondroFiller™. That group, where diffuse articular loss dominates, is precisely the population in which HA viscosupplementation or a corticosteroid for acute flare control may be the more appropriate consideration.

Conversely, the patient with an isolated focal defect and a structurally sound surrounding joint is not well served by a palliative lubricant or an anti-inflammatory — neither addresses the underlying structural gap.

No published randomised controlled trial has directly compared ChondroFiller™ to HA or corticosteroid. Given that the treatments serve different indications, designing such a trial is inherently difficult, but the evidence gap remains real and should temper any absolute claims about relative superiority.

For patients uncertain which category applies to them, MRI assessment of defect size and joint-wide cartilage health — alongside consultant review — is the necessary starting point.

What to ask at your consultation

Three questions, in particular, help clarify which injection pathway is relevant before any consultation ends.

Does the problem involve a focal defect or diffuse joint degeneration? This is the single most important diagnostic distinction. A focal cartilage lesion and widespread osteoarthritis are structurally different conditions, and — as the evidence in preceding sections makes clear — the injection options that follow from each differ in kind, not just degree. Imaging, usually MRI, is the tool that answers it reliably; clinical symptoms alone are not sufficient.

If a focal defect is confirmed, how large is it? Published clinical studies of ChondroFiller™ have focused on defects up to 6 cm². Defect size influences both treatment eligibility and the likely quality of the repair process, so having a measured assessment rather than an estimate matters.

What is the goal — short-term flare control, medium-term symptom management, or structural repair? These are genuinely different objectives. If corticosteroid injections have already been used three or more times in the same joint, the clinical priority generally shifts toward alternatives; repeated use carries documented risks to cartilage integrity that narrow the window for any subsequent regenerative approach.

A specialist with access to ultrasound and MRI can work through all three questions in a single assessment. This type of evaluation does not require a GP referral — patients can arrange it directly through a consultant-led service if they prefer not to wait for an NHS pathway.

1. [1] A Cross-Sectional Study of Factors Predicting the Duration of Efficacy of Viscosupplementation in Knee OA. (2024). https://doi.org/10.3390/jcm13071949 https://doi.org/10.3390/jcm13071949
2. [2] Radiographic Features and Duration of Effectiveness of Single Injection of Extended-Release HA (HANOX-M-XL) in Knee OA. (2022). https://doi.org/10.1177/19476035221109230 https://doi.org/10.1177/19476035221109230
3. [3] Arthroscopic utilization of ChondroFiller gel for the treatment of hip articular cartilage defects: 12- to 60-month follow-up. (2021). https://doi.org/10.1093/jhps/hnab002 https://doi.org/10.1093/jhps/hnab002
4. [4] Controlled, randomized multicenter study to compare compatibility and safety of ChondroFiller liquid with microfracturing. (2016). https://doi.org/10.5348/VNP05-2016-1-OA-1 https://doi.org/10.5348/VNP05-2016-1-OA-1