Arthritis and tendonitis affect a large part of the population. For people who play sports or run, the pain and swelling can stop them from participating altogether. One proven option is a hyaluronic acid injection — also called a gel injection or viscosupplementation. Dr Masci performs hyaluronic acid injections under ultrasound guidance at his London clinics, with one-stop appointments from £490.

So do gel injections work? Which type works best? And what should you expect? This guide answers the questions patients ask us most.

What is hyaluronic acid?

Hyaluronic acid occurs naturally in the body. It is a building block and source of nourishment for cartilage and bone, and it gives joint fluid its lubricating quality. You can take hyaluronic acid as a tablet, but it works far more effectively when injected directly into the joint.

How does a gel injection work?

We understand the mechanism partially. The gel lubricates the joint, allowing it to move more smoothly. It also reduces joint inflammation, pain, and swelling by binding to receptors in the joint lining. One thing we know for certain: hyaluronic acid does not regenerate cartilage. It treats symptoms, and it does so well.

Does the molecular weight of viscosupplementation matter?

Yes — this is the single most important factor when choosing a gel injection. Viscosupplementation comes in high and low molecular weights. High-molecular-weight products are more potent, last longer in the joint, and need only one injection.

In one study, high-molecular-weight hyaluronic acid worked at least twice as well as low-molecular-weight products. The Arthroscopy Association of Canada also recommends high-molecular-weight hyaluronic acid for knee and hip arthritis pain.

The ideal gel injection has three characteristics: high molecular weight, high cross-linking, and non-animal manufacture (which reduces the risk of reaction). Durolane meets all three criteria, which is why it is our preferred hyaluronic acid. Brands such as Ostenil Plus and Synvisc 1 do not.

What conditions do we treat with gel injections?

Knee arthritis has the strongest evidence and is the most common condition we treat with hyaluronic acid. We also inject:

In selected tendon problems, we use hyaluronic acid differently. In some cases of Achilles tendinopathy, the plantaris tendon rubs against the Achilles. Injecting hyaluronic acid between the two tendons reduces friction and improves pain.

Cortisone vs hyaluronic acid injections: which is better?

Cortisone injections relieve pain and swelling in knee arthritis, but the effect is small and short-lived. Cortisone also carries risks of cartilage damage, and we limit injections to 3 per joint per year.

Gel injections work differently. They take longer to act — up to 4 weeks — but the effect lasts much longer, often 12 months or more. They suit younger patients with milder arthritis best, although older patients with advanced disease can still benefit. For a detailed comparison, read our cortisone vs hyaluronic acid guide.

How long does a viscosupplementation injection last?

High-molecular-weight gel injections last 6 to 12 months — and often longer. A study of more than 700 Durolane injections found that a single injection lasted an average of 466 days, with some lasting more than 1,000 days. Repeat injections worked as well as the first for up to six doses, and 70% of patients reported satisfaction.

Why ultrasound guidance matters

Always have a gel injection under ultrasound guidance. Ultrasound ensures the hyaluronic acid lands inside the joint, not in the surrounding soft tissue. Gel injected outside the joint can cause severe pain and swelling.

The evidence backs this strongly. In a survey of over 1,000 patients receiving hyaluronic acid for knee arthritis, ultrasound-guided injections produced over 30% fewer knee replacements than blind injections. Ultrasound-guided patients were also 27% less likely to need a subsequent cortisone injection.

Dr Masci performs every gel injection under ultrasound guidance. He has performed thousands of ultrasound-guided injections and teaches injection techniques to doctors across the UK and Europe. Read about his injection expertise here.

How much do hyaluronic acid injections cost in the UK?

Hyaluronic acid injection prices in the UK vary widely between clinics. Dr Masci offers a one-stop ultrasound-guided hyaluronic injection at his Chelsea clinic for £470 — a single visit that includes consultation, diagnostic ultrasound, and injection. Prices apply to the Chelsea clinic; other clinic locations cost more. See our one-stop injection fees and clinic locations.

Because one high-molecular-weight injection lasts over a year on average, the cost per month of relief compares well with repeated low-molecular-weight courses.

Side effects of hyaluronic acid gel injections

Like all injections, gel injections carry side effects:

  • Mild pain and swelling after the injection, lasting 1–2 weeks (10–20%)
  • Allergic-type reaction within 1–2 days of the injection (1–2%)
  • Infection (around 1 in 10,000)

Animal-derived hyaluronic acid reacts more often, which is one reason we prefer non-animal products such as Durolane. After your injection, rest the joint for at least 48 hours and avoid prolonged standing or walking.

What about combining hyaluronic acid and PRP?

Evidence increasingly supports combining the two. A recent review found PRP plus hyaluronic acid beats PRP alone at 3, 6, and 12 months. Adding hyaluronic acid to PRP also reduces the risk of a post-injection flare. Read more about combined hyaluronic acid and PRP injections. This combination may well become the norm.

Frequently asked questions about viscosupplementation injections

Do gel injections in the knee hurt?

Not when performed under ultrasound guidance. A very painful gel injection has probably missed the joint, which also raises the risk of a severe reaction called pseudo-sepsis. Choose an experienced doctor who injects under ultrasound guidance, and avoid animal-based products.

Is Durolane more likely to cause a severe reaction than other hyaluronic acids?

Durolane is a high-molecular-weight product, so it is more potent, and we believe it carries a slightly higher reaction rate. However, the vast majority of reactions are mild and settle quickly. In our view, the longer-lasting benefit outweighs this small difference. Read more on Durolane side effects.

Can a gel injection go into the shoulder?

Yes. Dr Masci frequently injects hyaluronic acid for shoulder arthritis — in fact, Durolane is his preferred injection for the shoulder joint. The injection must target the joint accurately, which is why ultrasound matters.

What should I do after a gel injection?

Rest the joint for at least three days. Exercising too soon raises the risk of a reaction with pain and swelling. If a flare occurs, use ice and simple medication such as ibuprofen for 5–7 days. Most flares settle. If pain or swelling persists, see your doctor — occasionally we drain the joint and settle it with cortisone. Full post-injection care guide here.

Do gel shots raise blood sugar levels?

No. Unlike cortisone, hyaluronic acid does not affect blood sugar. This makes gel injections an excellent option for people with diabetes.

How often can I repeat a gel injection?

Every 6–12 months, for as long as they keep working. Studies show repeat injections stay as effective as the first for up to six doses. Unlike cortisone, hyaluronic acid does not damage the joint, so there is no strict upper limit.

My knee is worse after a gel injection. What should I do?

Short-term worsening sometimes happens. Use ice and oral anti-inflammatories such as ibuprofen. If the knee becomes very swollen and inflamed, you may have had an allergic-type reaction (1–2% of patients). Speak to your doctor — some knees need draining.

Is Arthrosamid the same as viscosupplementation?

No. Arthrosamid is a non-degradable polyacrylamide hydrogel, not a hyaluronic acid. The body does not break it down, and recent studies show that its benefits last at least 5 years. We consider Arthrosamid when hyaluronic acid has worn off or failed.

Which gel injection is right for you?

For most patients, we follow a simple ladder. We start with a single high-molecular-weight hyaluronic acid injection — Durolane, £490 — which helps around 70% of patients for a year or more. If hyaluronic acid fails or wears off, we consider ACP Max PRP or Arthrosamid. Dr Masci will examine your joint, review your imaging, and advise which option suits you at a single consultation.

Final word from Sport Doctor London about hyaluronic acid injections

Hyaluronic acid injections are a proven, long-lasting addition to arthritis treatment. The evidence is strongest for knee arthritis, and the choice of product matters: high molecular weight, highly cross-linked, non-animal. Always insist on ultrasound guidance.

To book a one-stop hyaluronic acid injection in London, contact Dr Masci’s team here or call +44 (0) 203 488 0350.

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