Arthritis and tendonitis are common in the general public. For those active in sports or running, arthritis and tendonitis can cause pain and swelling that stops us from participating in these activities. One option for treating arthritis and tendonitis is a hyaluronic acid gel or viscosupplementation injection. So, is a hyaluronic acid injection effective for arthritis and tendonitis?

What is hyaluronic acid?

Hyaluronic acid, also called viscosupplementation, is a naturally occurring substance in the body. It forms part of the building blocks and nourishment for cartilage and bone. You can consume hyaluronic acid as a tablet, but we think it works better if injected directly into a joint.

How does a hyaluronic acid gel injection work?

We are not entirely sure, but we have some ideas. One theory is that hyaluronic acid gel injection acts as a lubricant, so the joint works more smoothly. Alternatively, we think a gel injection reduces joint inflammation, pain, and swelling. However, we are sure that hyaluronic acid does not regenerate joint cartilage.

Does the molecular weight of hyaluronic acid matter? 

Generally, molecular weight refers to how heavy the hyaluronic acid molecules are. Viscosupplementation can be high molecular or low molecular weight. High molecular weight only needs one injection as it is more potent and lasts longer in the joint.

An example of a higher molecular weight hyaluronic acid is Durolane.

There is some debate about whether high or low molecular weight is better. However, recent evidence suggests that high molecular weight hyaluronic acid is better. In one study, the effect of high molecular weight was at least double the low molecular weight. In addition, the Arthroscopy Association of Canada suggests that high molecular weight hyaluronic acid demonstrates a good effect on knee and hip arthritis pain.

So what can be treated with viscosupplementation injection? 

The most common condition we treat with hyaluronic acid is knee arthritis. However, other conditions are also treated, including:

Overall, the most evidence is in gel injections for knee arthritis.

Cortisone vs hyaluronic acid injections for knee pain: which is better

We know that cortisone injections improve pain and swelling in knee joint arthritis. However, the effect of cortisone is small and short-lived. Additionally, we have several concerns about side effects, such as cartilage damage. Also, there are limits to the number of cortisone injections. Generally, we recommend no more than three injections into one joint over 12 months.

Gel injections offer a different option. Generally, hyaluronic acid injections take longer to work than cortisone (up to 4 weeks), but the effect is often longer-lasting – up to 12 months. However, these shots are not for everyone. Research suggests that the evidence of effectiveness is mixed. They seem to work better for younger patients with less advanced arthritis. Moreover, older patients with more advanced diseases are less likely to experience pain relief.

There are different brands of viscosupplementation. We are not sure which brand is the best. However, some groups suggest the best form of hyaluronic acid has the following characteristics:

  • high molecular weight
  • high cross-links
  • non-animal products

High molecular weight means that hyaluronic acid works better. Non-animal product means that the reaction rate is lower. The brands with these characteristics include Durolane. Other brands like Ostenil Plus or Synvisc 1 do not have these characteristics.

How long does a viscosupplementation injection last?  

Generally, the higher concentration gel injections last from 6 to 12 months.

A recent study sheds light on how long Durolane injections last. Generally, the effect of one single injection lasted, on average, about 466 days. However, in some cases, Durolane lasted for greater than 100 days. Also, subsequent injections lasted as long as the first injection for up to 6 injections. Finally, 75% of people who had a Durolane injection were satisfied.

Are there other points to consider about gel shots for knee arthritis?

Usually, people consider these gel injections when they fail to exercise tablets and cortisone injections. For example, some people can’t take common anti-inflammatories like ibuprofen due to stomach ulcers or previous heart attacks. In addition, as the side effects of viscosupplementation injections are minimal, some people consider these injections an alternative to surgery.

You need to understand that a gel injection should be done with an ultrasound. Ultrasound ensures that hyaluronic acid is injected into the joint, not outside. If you inject hyaluronic acid into the soft tissue, there is a chance that you may experience severe pain and swelling. A recent study shows that a hyaluronic acid injection performed with ultrasound has a much better effect than blind injections (without ultrasound). In a survey with over 1000 patients who had hyaluronic acid injections for knee arthritis, those who had injections with ultrasound had much fewer rates of knee replacement (over 30% less) than those who had blind injections. Moreover, patients with an ultrasound-guided hyaluronic acid injection were 27% less likely to need a subsequent cortisone injeciton for pain.

Recently, a new type of injection called platelet-rich plasma or PRP has shown more promise in arthritis. PRP is taken from whole blood and spun down, separating the plasma from the red cells. As a result, the plasma contains many growth factors and platelets. Recent studies suggest PRP may be better than hyaluronic acid or cortisone for knee arthritis.

Platelet-rich plasma injections - alternative to cortisone injection in shoulder

Side effects of hyaluronic acid gel injections?  

Like all medications, gel injections have side effects. You need to speak to your doctor about these side effects. The most common side effects include pain at the injection site, fluid build-up in the knee, and allergic reactions. Generally, you should use other options if you have an allergy to hyaluronic acid-based products. For example, in a recent study on Durolane injections, the rate of allergic reactions is between 2 and 3%. Also, we know hyaluronic acid made from animal products is more likely to react.

Usually, after a hyaluronic acid gel injection, you need to rest the joint for at least 48 hours. Also, you should avoid prolonged standing or walking.

What about combining hyaluronic acid and PRP?

So, there is some evidence that combining PRP and hyaluronic acid is better than one.

A recent review found that combining PRP with hyaluronic acid is better than PRP alone. This positive effect was found at 3, 6, and 12 months. Also, adding hyaluronic acid to PRP reduces the risk of a flare after a PRP injection.

Perhaps this combination will be the norm in the future.

Another use in plantaris-associated Achilles tendinopathy 

Some cases of Achilles tendinopathy have a plantaris tendon interfering with the inside of the Achilles tendon. Some people have a specific type of anatomy that encourages friction between the two tendons. Recent evidence suggests that hyaluronic acid injected between the two tendons reduces this friction and improves pain.

Frequently asked questions about viscosupplementation injections:

Do gel injections in the knee hurt? 

Generally, no if the knee injection is done with ultrasound guidance. If a knee gel injection is excruciating, it probably has not gotten into the joint. Also, failing to get in the joint means the risk of a severe reaction such as ‘pseudo-sepsis’ increases. Getting an experienced doctor to do your ultrasound-guided injection would be best. These are four questions you should ask before you have an ultrasound-guided injection.

Also, you should avoid animal-based hyaluronic acid due to the higher chance of an allergic reaction.

I’ve heard that Durolane is more likely to cause a severe reaction than other types of hyaluronic acid. Is this true? 

Not really. Durolane is a high molecular weight hyaluronic acid, which is more potent. We think that it also has a slightly increased reaction rate. The vast majority of these reactions are mild and settle quickly.

Can synvisc be injected into the shoulder? 

Yes, but the shoulder joint should be the target. However, there is less evidence for a gel shot in shoulder arthritis.

What should I do after a Synvisc injection? 

Generally, we suggest you rest the joint for at least three days after a gel shot. Exercise after injection increases the risk of a reaction, including pain and swelling.

We suggest ice and simple medication such as ibuprofen for 5-7 days if you get a reaction. Most cases settle in time. However, you should see your doctor if your knee pain or swelling doesn’t resolve. Occasionally, we might need to drain the swelling and inject cortisone into the knee to settle it.

Does Synvisc raise blood sugar levels? 

No. Gel shots do not affect blood sugar levels, meaning they are entirely safe for people with diabetes.

How long does gel injection in the knee last?

Generally, the viscosupplementation injections should last up to 12 months with the higher molecular weight hyaluronic acid. Therefore, we think having a repeat injection every 6-12 months is safe. However, one recent study found that HA injections lasted 450 days, and some lasted more than 1000 days. In that same study, repeated shots continued to work as the first shot for up to 6 shots.

Knee gel injection side effects: Are they common? 

Like any joint injection, there are side effects with viscosupplementation injections. These side effects include:

  • Mild pain and swelling after a knee gel injection, which lasts for 1-2 weeks (10-20%)
  • Severe allergic reaction that occurs within 1-2 days after an injection (2-3%)
  • infection (1:10000)

My knee pain is worse after gel injection. What do you do? 

Sometimes, gel injections could worsen the pain. This increase in pain may be short-term only. We suggest anti-inflammatory measures such as ice and oral NSAIDs (ibuprofen).

However, in some cases, the knee becomes swollen and inflamed. In these cases, you might have experienced an allergic reaction. About 2-3 % of patients have an allergic reaction. You should speak to your doctor if you’ve experienced an allergic reaction. In some cases, you’ll need to have the knee drained.

I’ve heard of this new hydrogel called Arthrosamid. Is this injectable the same as viscosupplementation? 

No, Arthrosamid is not a hyaluronic acid.

Arthrosamid is a unique hydrogel of water molecules attached to a polyacrylamide backbone. The injectable is non-degradable, meaning the body does not break it down. It works by coating the lining of the synovium of the knee joint, reducing inflammation, and providing lubrication. Recent studies show improvement in pain scores lasting for up to 2 years. In addition, compared to hyaluronic acid, it works better in younger and slimmer patients.

Final word from Sportdoctorlondon about hyaluronic acid injection

Overall, hyaluronic acid injections are a helpful addition to treatment for arthritis. Generally, the best evidence is in knee arthritis, although injections into other joints are possible.

More injection information:

Dr Masci is a specialist sports doctor in London. 

He specialises in muscle, tendon and joint injuries.

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