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Published on
29/10/2026
The LivingCare Group
The evidence does not settle it either way. A two-year trial found more cartilage loss (0.11 mm over two years) in knees injected every three months, and an observational study linked a single injection to more change on MRI. Neither shows that an occasional injection damages a joint. On knee replacement, a national study from England and an earlier study by researchers in the Netherlands point in opposite directions.
All four studies below looked at knee osteoarthritis, and osteoarthritis itself is widespread. Arthritis UK's State of Musculoskeletal Health 2025 report states that "10 million adults have a probable diagnosis of osteoarthritis" [1]. That is an age-standardised estimate, not a count of confirmed diagnoses. This article sets out what the main studies found, what they did not test, and where that leaves a decision about an injection.
A steroid injection places a corticosteroid medicine into or around a painful joint. For osteoarthritis, NICE's guideline sets out when one may be considered: "Consider intra-articular corticosteroid injections when other pharmacological treatments are ineffective or unsuitable, or to support therapeutic exercise. Explain to the person that these only provide short-term relief (2 to 10 weeks)." [2]
Intra-articular means into the joint itself. LivingCare's Steroid Injections and Joint Injections pages explain how the treatment works at LivingCare.
The main randomised evidence on repeated injections is a trial published in JAMA in 2017 [3]. In it, 140 people with knee osteoarthritis had either a steroid (triamcinolone) or a saline placebo (dummy) injection into the knee every three months for two years - eight injections in all [3].
After two years, cartilage thickness had fallen by 0.21 mm in the steroid group and by 0.10 mm in the saline group, a difference of 0.11 mm [3]. There was no significant difference in knee pain between the two groups [3].
The detail matters as much as the headline:
A study published in the journal Radiology in May 2025, after peer review, linked a single steroid injection to more change in the knee on MRI [4]. It was first presented at the Radiological Society of North America (RSNA) annual meeting in 2022.
The researchers drew on a long-running observational study, the Osteoarthritis Initiative. They compared 44 knees that had one steroid injection, 26 that had one hyaluronic acid injection and 140 matched knees that had neither, over the two years before and two years after the injection [4]. Knees given a steroid injection showed more progression on a whole-knee MRI score than both comparison groups [4].
The paper's authors state: "Given the observational study design, it was not possible to establish a causal relationship between intra-articular injections and progression of knee OA. Uncontrolled confounding and confounding by indication between cases, controls, and types of intra-articular injections may account for the differences observed between groups." [4]
Confounding by indication means the people who are offered an injection may already differ from those who are not - in how severe or active their arthritis is, for example - so a difference between the groups may reflect who was injected rather than the injection itself.
A national study from England, published in BMC Medicine in 2025 and funded by the National Institute for Health and Care Research, measured a different outcome: knee replacement surgery rather than MRI scores [5]. It followed 33,357 people with knee osteoarthritis. Its main analysis linked a single injection to an "approximate halving in rates of knee replacement" over one or five years [5].
That is not a clean reassurance either. The authors conclude that short-term pain reduction after an injection "may translate to lower rates of knee replacement over 5 years follow-up, although contradictory associations were observed in secondary analyses which likely reflected residual confounding by indication." [5] It is the same caveat as the MRI study, from the other direction.
An earlier study points the opposite way. Researchers in the Netherlands, publishing in The Bone & Joint Journal in 2020, drew on data from the same long-running Osteoarthritis Initiative as the MRI study, covering 3,822 people with, or at risk of, knee osteoarthritis followed for up to nine years [6]. They matched people who had steroid injections with similar people who had not. In that matched analysis, the rate of knee replacement was just over one and a half times higher in people who had injections (a hazard ratio of 1.57) [6]. The authors conclude that the injections "seem to be associated with an increased risk of knee arthroplasty" - the medical term for joint replacement [6].
So two observational studies of the same outcome point in opposite directions, and neither can show that the injection itself made the difference.
Put together, these studies leave real gaps:
The fairest summary is that the randomised evidence on repeated knee injections found a measurable difference in cartilage (0.11 mm) whose importance to patients is not yet defined, and the observational evidence points in different directions, even when the same outcome is measured.
There is a common convention, but not an evidence-based limit. A 2026 practice article in the Canadian Medical Association Journal describes repeat injections as "generally limited to 3 to 4 times per year, per joint", and states in the same passage that "no evidence-based recommendations exist for repeat injection number and frequency" [7].
The NHS, writing about hydrocortisone injections, puts it this way: "The number of injections you can have depends on the area being treated and how strong the dose is." [8] So the number is decided case by case [8].
The NHS lists side effects for hydrocortisone injections [9]. Hydrocortisone is one steroid; knee injections often use others, such as triamcinolone or methylprednisolone [7], so read this as a general guide rather than a list for any one injection:
The risks of the specific injection being considered are part of the consultation.
With a conversation rather than a rule. These studies describe groups of people; they cannot say what an injection would mean for one person's joint. At a consultation, a pain specialist weighs how often injections have been given, which joint is involved, the alternatives, and what the evidence above does and does not show. For the knee in particular, see Knee Arthritis, and our article How Long Does A Knee Injection Last? for what the evidence reports on duration.
Does a single steroid injection damage the joint? The evidence does not show that it does, or that it does not. One observational study linked a single knee injection to more change on MRI over four years, but its authors say it could not establish cause and effect [4]. A national study from England linked a single injection to lower rates of knee replacement, with its own caveat about confounding [5].
Did the knees in the MRI study have less pain after the injection? The authors report that both the steroid and the hyaluronic acid injections were "associated with reduced pain (WOMAC) postinjection" [4]. WOMAC is the questionnaire score the study used to measure pain. This is the same observational study whose authors say it cannot show cause and effect.
Does a steroid injection affect a later knee replacement? The national study from England found similar rates of complications after knee replacement whether people had had no injection, a single injection or repeated injections beforehand [5]. The 2026 practice article states that "injections should be avoided at least 3 months before joint replacement" [7].
If you have been offered a steroid injection, or are considering one, and want to understand what the evidence means in your case, a Pain Management Consultation is where that conversation happens. Consultations run at Thorpe Park Clinic in Leeds and Canon Medical Arena in Sheffield. Exceptional care, without the wait.
Medically reviewed by: Mr Paul Sutton, Consultant Orthopaedic Surgeon
This article is for general information and is not sponsored content.
