Hyaluronic Acid Injections for Knee Arthritis: What the Studies Show

Hyaluronic acid injections, often called “gel shots” or viscosupplementation, are one of the most common treatments for knee arthritis, and one of the most debated. Here is a plain summary of what the studies show, so you can decide with your doctor whether they make sense for you.

What hyaluronic acid is

Hyaluronic acid is a natural part of the fluid that lubricates and cushions your joints. In arthritis, that fluid becomes thinner. The injection places a purified form of hyaluronic acid directly into the knee. Depending on the product, treatment is a single injection or a short series of weekly injections.

What the studies show

• Many patients improve. A Cochrane review of 76 trials found that pain improved 28% to 54% from where patients started, measured 5 to 13 weeks after injection.

• Relief tends to come gradually and last longer than a steroid shot. In a pooled analysis of trials comparing the two, steroid injections worked faster in the first few weeks. By week 4 the two were equal, and from week 8 through 6 months hyaluronic acid did better.

• Many patients count as clear “responders.” A sports medicine society review that counted patients who met standard improvement criteria found that people who received hyaluronic acid were 15% more likely to respond than those who received a steroid and 11% more likely than those who received a placebo injection. In one 6-month study of a single-injection product, about 60% of patients met those criteria at 4 weeks, rising to about 65% at 6 months.

• The added benefit over a placebo injection is debated. The largest review, 169 trials and over 21,000 patients published in 2022, found that the average extra pain relief compared with a saltwater (placebo) injection was small, below what is usually considered clinically important. That review also reported a higher rate of serious adverse events in the hyaluronic acid groups, though these events are uncommon.

The bottom line: many patients get good relief after hyaluronic acid injections, often lasting several months. How much of that comes from the hyaluronic acid itself, rather than the injection and the natural ups and downs of arthritis, is still debated.

Who tends to do best

Response varies from person to person. In one study, 87% of patients without marked joint-space narrowing or obesity met the response criteria, compared with 42% of patients who had both. In general, people with mild to moderate arthritis tend to respond better than those with bone-on-bone arthritis.

Hyaluronic acid may be worth considering if you:

• Still have knee pain despite exercise and other first-line treatments

• Can’t take anti-inflammatory pills because of stomach, kidney or heart concerns

• Want to limit repeated steroid injections

• Are not ready for, or not a candidate for, knee replacement

What the guidelines say

Expert groups disagree, which reflects how mixed the evidence is:

• American Academy of Orthopaedic Surgeons (2021): not recommended for routine use, while noting it can be a viable option for some patients who have not improved with other treatments.

• American College of Rheumatology (2019): conditionally recommends against it for the knee.

• Osteoarthritis Research Society International (2019): a conditional option for some patients, depending on their other health conditions.

• European expert groups (ESCEO): support it as an option for knee arthritis, outside of acute flares.

• UK NICE (2022): advises against offering it.

Safety

Most people tolerate these injections well. The most common side effects are temporary pain, swelling or stiffness in the knee for a day or two. Serious reactions and joint infection are uncommon. Insurance coverage varies by plan, so it is worth checking before treatment.

Part of a bigger plan

Injections work best as part of a broader plan, not on their own. Strengthening the muscles around the knee remains the foundation of arthritis care. You can read about our approach in Stronger Knees Are Functional Knees. If you are wondering whether hyaluronic acid is right for your knee, book a visit and we can review your options together.

References

• Bellamy N, et al. Viscosupplementation for the treatment of osteoarthritis of the knee. Cochrane Database Syst Rev. 2006;(2):CD005321.

• Bannuru RR, et al. Therapeutic trajectory of hyaluronic acid versus corticosteroids in the treatment of knee osteoarthritis. Arthritis Rheum. 2009;61(12):1704-1711.

• Trojian TH, et al. AMSSM scientific statement concerning viscosupplementation injections for knee osteoarthritis. Br J Sports Med. 2021.

• Bruyère O, et al. Is the rate of responders to hyaluronic acid injection for patients with knee osteoarthritis stable over time? Rheumatol Ther. 2023.

• Pereira TV, et al. Viscosupplementation for knee osteoarthritis: systematic review and meta-analysis. BMJ. 2022;378:e069722.

• Conrozier T, et al. Impact of obesity, structural severity and their combination on the efficacy of viscosupplementation in patients with knee osteoarthritis. BMC Musculoskelet Disord. 2019.

• American Academy of Orthopaedic Surgeons. Management of Osteoarthritis of the Knee (Non-Arthroplasty) Clinical Practice Guideline, 3rd ed. 2021.

• Kolasinski SL, et al. 2019 ACR/Arthritis Foundation guideline for the management of osteoarthritis of the hand, hip, and knee. Arthritis Care Res. 2020;72(2):149-162.

• Bannuru RR, et al. OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis. Osteoarthritis Cartilage. 2019;27(11):1578-1589.

• Fuggle N, et al. Expert consensus on hyaluronic acid injections for knee osteoarthritis (ESCEO). 2026.

• National Institute for Health and Care Excellence. Osteoarthritis in over 16s: diagnosis and management (NG226). 2022.