Hyaluronic acid is not a steroid. It is a polysaccharide, which is a type of sugar molecule, and it belongs to a class of compounds called glycosaminoglycans. Steroids like cortisone have a completely different chemical structure built around rings of carbon atoms and work by suppressing inflammation. Hyaluronic acid works by retaining water and providing lubrication. The confusion usually comes up because both substances are injected into joints to treat osteoarthritis pain, but they are fundamentally different compounds with different mechanisms.
What Hyaluronic Acid Actually Is
Hyaluronic acid is a long chain of repeating sugar units, specifically D-glucuronic acid and N-acetylglucosamine linked together. Your body produces it naturally. It’s found in high concentrations in your joints, skin, and eyes, where its primary job is holding onto water. A quarter-teaspoon of hyaluronic acid can hold roughly one and a half gallons of water, which is what makes it so effective as a lubricant and moisturizer.
In your joints, hyaluronic acid acts like a cushioning fluid that prevents bones from grinding against each other. In your skin, it helps maintain elasticity and reduces the appearance of wrinkles. In your eyes, it helps retain moisture. When people with osteoarthritis lose hyaluronic acid in their joint fluid, injecting more of it is meant to restore that natural cushioning rather than suppress the immune system the way a steroid would.
How Steroids Work Differently
Corticosteroids like cortisone are synthetic versions of hormones your adrenal glands produce. They reduce inflammation by dampening your immune system’s activity in the area where they’re injected. This is why steroid injections can provide fast pain relief for inflamed joints, but it’s also why they come with side effects that hyaluronic acid doesn’t share. Repeated corticosteroid injections can thin nearby skin and fat tissue, cause facial flushing, and over time may even weaken cartilage in the joint.
Hyaluronic acid side effects are generally limited to mild, short-lived reactions at the injection site: temporary pain, swelling, or tenderness. It doesn’t carry the systemic risks associated with steroids because it isn’t altering your immune response or hormone levels. It’s simply adding back a substance your body already makes.
Why Both Are Used for Knee Pain
The overlap that causes confusion is that both hyaluronic acid and corticosteroid injections are common treatments for osteoarthritis of the knee. They’re both given as shots directly into the joint, often by the same types of doctors, for the same condition. But the treatment experience differs.
Corticosteroid injections are typically a single shot that can start relieving pain within days. Hyaluronic acid injections often involve a course of three weekly injections, and the relief builds more gradually. In clinical comparisons, both treatments produced similar improvements in pain and function at three and six months, with no significant differences between the two groups. So the choice between them often comes down to how quickly you need relief and how you respond to each option individually.
One practical difference: corticosteroid injections are generally limited to a few times per year in the same joint because of the risk of cartilage damage with repeated use. Hyaluronic acid doesn’t carry that same restriction, which makes it an option for people who need ongoing treatment or who want to avoid steroids for other reasons.
How the FDA Classifies Hyaluronic Acid
Interestingly, hyaluronic acid joint injections have been regulated by the FDA as medical devices rather than drugs. This is unusual for something you inject into the body, and the FDA has signaled it may reconsider this classification. The agency noted that current scientific literature supports the idea that hyaluronic acid achieves its pain-relieving effects through chemical action in the body, which would make it more consistent with the definition of a drug. This regulatory nuance doesn’t change what hyaluronic acid is or how it works, but it does mean the approval pathway for these products has been different from typical medications.
Outside of joint injections, hyaluronic acid appears in skincare serums, eye drops, and dermal fillers. In these forms it’s used purely for its water-retention properties. None of these applications involve any steroid-like activity.
Key Differences at a Glance
- Chemical class: Hyaluronic acid is a polysaccharide (sugar chain). Steroids are built from carbon ring structures derived from cholesterol.
- How they work: Hyaluronic acid lubricates and cushions by retaining water. Steroids suppress inflammation by reducing immune activity.
- Naturally in your body: Hyaluronic acid is found in joints, skin, and eyes. Corticosteroids mimic hormones from your adrenal glands.
- Side effect profile: Hyaluronic acid causes mild, local reactions. Steroids can thin tissue, cause flushing, and carry risks with repeated use.
- Treatment schedule: Steroid injections are typically a single shot. Hyaluronic acid often requires a series of three injections over consecutive weeks.