PATIENT INFORMATION Hyaluronic acid injection: Synovial®(32 and 64) and Ostenil®
(Last update: June 2025)
What is hyaluronic acid injection?
Hyaluronic Acid (HA) injections (viscosupplements) are injectable agents which are used to treat the symptoms of mild to moderate osteoarthritis. This leaflet gives you some basic information about synovial joints, about what happens when you get osteoarthritis and about hyaluronic injections.
Nevertheless, sonography guided HA injection may help on other foot pathologies such as
Morton Neuroma, insertional Achilles tendinopathy injecting the substance inside the retrocalcaneal bursa, management of mid-portion Achilles tendinopathy or other tendinopathies on the foot.
What is a Synovial joint?
A synovial joint is one in which the ends of the bones are enclosed in a capsule containing a thick, slippery liquid called synovial fluid. The bone ends are covered in a smooth layer of a tough, rubbery substance called cartilage. The synovial fluid helps protect the cartilage from wear and tear by keeping the bones slightly apart and by acting as a shock absorber and lubricant. It also acts as a filter, letting nutrients reach the cartilage, but blocking the passage of harmful cells and substances. The most important component of synovial fluid is a substance called hyaluronic acid. It is this substance that allows the synovial fluid to perform its cartilage saving properties. Hyaluronic acid is continuously broken down and replaced. Normally, there is an exact balance between the breakdown of old hyaluronic acid and the production of new hyaluronic acid. In osteoarthritis, however, this balance is disturbed and breakdown happens faster than production. As a result, the synovial fluid becomes watery and stops working properly. As a result the cartilage in the joint gradually wears away. The thinning of the synovial fluid and wearing away of the cartilage leads to symptoms of osteoarthritis, which include pain, stiffness and swelling.
How do Hyaluronic Acid Injections work?
Injections can:
- Improve the viscosity of the synovial (lubricating) fluid.
- Reduce pain and swelling within the joint.
- Increase the articular cartilage depth on load bearing surfaces.
- These products can provide symptom relief but do not cure the underlying osteoarthritic disease process. The technique of supplementing the hyaluronic acid levels in a joint is called Viscosupplementation.
- Hyaluronic acid (HA) injections support tendon healing by improving tendon gliding, reducing friction and inflammation, and promoting the formation of healthy collagen
What brands of Hyaluronic Acid Injections do you administer?
In some occasion, we may offer Ostenil Mini or Plus (is used to treat small joints such as in the foot). But we use mainly Sinovial HL 32 and 64.
Treatment of Ostenil mini usually involves a course of up to 3 injections. Ostenil Plus is used to treat larger joints such as ankle joint. Ostenil Plus contains sodium hyaluronate along with 0.5% mannitol, a free radical scavenger which helps to stabilise the sodium hyaluronate chains thus increasing their residence time in the joint. Treatment with Ostenil Plus usually involves a single injection.
Ostenil Tendon® injections use a specialised hyaluronic acid solution to reduce pain, improve mobility, and support healing in foot and ankle tendinopathies—such as Achilles and tibialis posterior tendon issues.
Sinovial HL 32 is a 1ml injection and used to treat small joints with osteoarthritis or tendinopathies. It is the highest concentration available in the UK at 32mg per ml (3.2%) and is usually a single injection, though your clinician may inject up to 3 injections spaced over 3 weeks. It contains highly purified high and low molecular weight hyaluronic acid, stabilised with hydrogen bonds which improves the residence time. The patented molecular structure makes it lower viscosity, making the injection easier than other products and a more comfortable injection procedure.
Sinovial HL 64 is a 2ml injection used to treat medium to large joints with osteoarthritis or tendinopathies. It is the highest concentration available in the UK at 32mg per ml (3.2%) and is usually a single injection, though your clinician may inject up to 3 injections spaced over 3 weeks. It contains highly purified high and low molecular weight hyaluronic acid, stabilised with hydrogen bonds which improves the residence time. The patented molecular structure makes it lower viscosity, making the injection easier than other products and a more comfortable injection procedure.
How are the injections given?
The area around the joint is prepared with anti-septic solution, and the injection done under aseptic conditions. An area of skin and the tissues underneath are numbed with some local anaesthetic – this may sting a little. A needle is inserted into the joint space, the Sinovial HL 64 or 32 injected, and then the needle is withdrawn. Please report any known allergies (drugs, elastoplast etc) to the practitioner prior to the procedure.
What happens after the injection?
You may notice some redness and warmth in the joint after an injection. You may continue with your normal everyday activities, but strenuous use of the joint should be avoided for 1 week.
In the event of an Ostenil tendon® injection, you may experience mild soreness for a few days. Paracetamol can be taken to help alleviate discomfort. In more persistent tendon problems, a second injection may be recommended about a week later.
How long does do the benefits of Hyaluronic acid injections last for?
Although a minority of patients do not respond to treatment, patients with mild to moderate osteoarthritis often seen improvements in symptoms lasting around 6 to 12 months. However, this can vary from individual to individual. It should be noted however that patients with severe destructive osteoarthritis are far less likely to respond to treatment with these products, and for these patients, surgical joint replacement may offer the best solution. There are a number of viscosupplement preparations on the market. We have chosen to stock Sinovial HL based on clinical studies. Sinovial HL has been compared to 2% high molecular weight injections (such as Ostenil plus, Sinovial One), steroid injections and placebo injections, with quicker relief from pain and longer acting pain relief than all other products it has been compared to. It market leads in Italy and Switzerland as it is very well tolerated by patients. For patients who do respond to treatment with hyaluronic acid, injections may be safely repeated. There are no known long-term adverse effects with repeated injections of these products.
What are the possible risks and side effects of the treatment?
The risk of a complication arising from Sinovial HL® is low and serious complications are extremely rare. However occasionally the following may occur and may require medical attention:
- Some individuals are susceptible to fainting during medical procedures. Faints result from a sudden short-term fall in blood pressure. Please inform the podiatrist in advance if you feel this may be likely so that precautions can be taken.
- Some patients experience deterioration in their symptoms for about 48 hours after the injection. Rest and simple pain killers usually help.
- Infection may be introduced into the joint or soft tissues as a result of an injection. This is extremely rare but can have very serious consequences if not identified and treated promptly. If you experience progressive warmth, swelling or worsening symptoms at the injection site particularly in association with fever, seek urgent medical attention.
- Allergy is rare and the products we use are associated with a lower risk of allergy than some other viscosupplement products on the market. Any serious allergic reactions (if they occur) are most likely to occur within 20 minutes of the injection. Therefore, you should remain in the clinic for 20 minutes following your procedure.
- Bleeding or bruising. This is more likely if you are taking certain medications for example aspirin, warfarin or other antiplatelet drugs and usually settles with simple pressure. If you experience severe swelling or bruising after the injection seek urgent medical attention.
Still not sure:
For more information to see if you are candidate to HA injection or to book an appointment, please contact our practice at 07714792424 or info@sonopodiatry.co.uk
Acknowledgment: Sincere thanks to Dr. James Inklebarger for his initial assistance in providing some of the information