Knee Steroid Injections: What the Triamcinolone-vs-Saline Trial Found on Cartilage and Pain

The short answer

In a 2-year randomized trial published in JAMA in 2017, Timothy McAlindon and colleagues at Tufts Medical Center gave patients with knee osteoarthritis an intra-articular injection every 12 weeks of either 40 mg triamcinolone, a corticosteroid, or saline. The steroid group lost significantly more knee cartilage over two years, and its pain scores were no better than the saline group's. The authors concluded the findings "do not support this treatment" as a scheduled regimen for symptomatic knee osteoarthritis.

What the trial actually tested

This was a double-blind, randomized, placebo-controlled study, the design that best separates a drug's effect from the natural ups and downs of a chronic joint disease. The team enrolled 140 adults, randomized 70 to each arm, and 119 of them (85 percent) completed the full two years. Participants had a mean age of 58, and 54 percent were women. To qualify, they needed symptomatic knee osteoarthritis with Kellgren-Lawrence grade 2 or 3 changes on x-ray plus ultrasound evidence of synovitis, meaning an inflamed joint lining, the kind of knee where a steroid shot is often considered a reasonable option.

The comparator matters. Saline is not a true nothing; injecting fluid into a joint and the ritual of a procedure can both move pain scores. Testing triamcinolone against saline rather than against no treatment sets a demanding and honest bar: the steroid has to beat the placebo response, not merely the effect of doing nothing.

The cartilage finding

The primary imaging outcome was cartilage volume in the index compartment of the knee, measured by MRI. Over two years, the triamcinolone group lost about 0.21 mm of cartilage thickness, while the saline group lost about 0.10 mm. The between-group difference was roughly 0.11 mm (95 percent confidence interval about 0.20 to 0.03 mm; P = .01), meaning the steroid arm lost about twice as much and the gap was statistically significant.

Two cautions belong next to that number. First, 0.11 mm is a small absolute amount, and this trial was not designed to show that it translates into worse function, more surgery, or faster clinical decline. It measured structure on a scan, not a patient's future. Second, the mechanism is biologically plausible rather than proven here: corticosteroids can blunt inflammation but may also affect cartilage cell metabolism, which is one proposed reason repeated dosing could accelerate thinning. The trial documents an association with more volume loss; it does not by itself establish long-term harm to the joint.

The pain finding

The pain result is, in some ways, the more decisive one. On the WOMAC pain scale, both groups improved modestly, and the difference between them was not statistically significant (between-group difference about 0.64 units; 95 percent confidence interval roughly 1.6 to 0.3; P = .17). In plain terms, quarterly triamcinolone did not deliver better pain control across two years than quarterly saline.

That is the crux. A patient accepting repeated injections is trading something (cost, clinic visits, a small structural signal) for an expected benefit. In this trial, on this schedule, the expected pain benefit over placebo did not materialize.

What this trial does and does not overturn

It would be a misreading to conclude that steroid shots never help a knee. A single, well-timed intra-articular corticosteroid injection has good evidence for short-term relief of a flaring, inflamed joint, and the 2019 American College of Rheumatology and Arthritis Foundation guideline recommends intra-articular glucocorticoid injection for knee osteoarthritis, largely on that short-term basis. The McAlindon trial does not contradict that. What it challenges is a specific practice: giving the injection every 12 weeks, on a calendar, over years, in the hope of sustained control or disease modification. For that regimen, the trial found no pain advantage and a structural downside.

The distinction between "a shot for a bad flare" and "a shot every quarter indefinitely" is where this study earns its place. It is a reminder that a treatment can be genuinely useful for a short-term problem and yet fail to justify open-ended repetition.

Reading the numbers honestly

A few limits keep this in proportion. The trial ran two years, so it cannot speak to a single injection or to five years of use. It enrolled patients with ultrasound-confirmed synovitis, so results may differ in knees without active inflammation. The cartilage endpoint is a surrogate: meaningful, but not the same as pain, mobility, or the need for a joint replacement. And confidence intervals mean the true effects sit within a range, not at a single tidy value. None of that erases the headline. It sharpens it: more cartilage loss, no pain payoff, for scheduled quarterly dosing.

The practical takeaway

For anyone weighing repeated steroid injections for knee osteoarthritis, this trial is a strong argument to treat them as a targeted tool rather than a standing subscription, and to revisit the plan if shots are being stacked quarter after quarter without clear, lasting benefit. Whether and when to inject a given knee is an individual decision that depends on the joint, the symptoms, and the alternatives, and it belongs with a treating clinician who can see the whole picture. This article is educational and is not medical advice.