Arthrosamid® in Knee Osteoarthritis: Cushioning the Joint, Targeting Synovitis, and Partnering with Regenerative Medicine

Introduction

Knee osteoarthritis (OA) is one of the most disabling musculoskeletal conditions worldwide. It develops gradually, with a mix of cartilage wear, subchondral bone changes, ligament stress, and—importantly—inflammation of the joint lining (synovitis).

For years, treatments were limited to pain relief with medications, corticosteroid injections, and eventually joint replacement surgery. But in the last decade, orthobiologics—such as platelet-rich plasma (PRP) and mesenchymal stem cells (MSCs)—have opened up regenerative pathways. Alongside these advances, Arthrosamid®, a new injectable hydrogel, is emerging as both a standalone treatment and a partner to biologics and surgery.

The Synovium and Synovitis: Why They Matter

The synovium is the thin tissue lining inside the knee joint. It produces synovial fluid, which lubricates the cartilage and nourishes the joint.

• In healthy knees, the synovium is smooth and quiet.
• In osteoarthritis, the synovium often becomes inflamed—a condition called synovitis.

Synovitis leads to:

• Excess joint fluid → swelling and stiffness.
• Release of inflammatory mediators → pain and further cartilage damage.
• Strong association with worse symptoms and faster OA progression【Scanzello & Goldring, 2012】【Hill et al., 2007】.

Patients with synovitis-driven OA are often the ones who experience disproportionate pain and swelling, even with mild or moderate cartilage wear.

What Is Arthrosamid®?

Arthrosamid® is a polyacrylamide hydrogel (PAAG). Unlike hyaluronic acid injections that are gradually absorbed, Arthrosamid® is non-resorbable. After injection, it integrates with the synovial lining, becoming part of the joint’s cushioning structure.

Its effects include:

• Reducing friction within the knee.
• Stabilising the inflamed synovium, reducing pain from synovitis.
• Providing a long-lasting cushion, improving shock absorption.

In essence, Arthrosamid® acts as a permanent biomechanical scaffold inside the joint.

Clinical Evidence

• Randomised controlled trial (Tetsworth et al., 2018, Osteoarthritis & Cartilage) – Arthrosamid® significantly improved pain and function over placebo, with effects sustained for 2 years.
• 4-year prospective study (Larsen et al., 2021, KSSTA) – Many patients continued to benefit from a single injection up to 4 years later.
• Safety – The most common side effects are mild swelling or soreness at the injection site; no major treatment-related adverse events have been reported.

Compared with hyaluronic acid, which typically lasts 3–6 months【Bannuru et al., 2019】, Arthrosamid® provides multi-year durability.

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Where Arthrosamid® Fits

1. As an Alternative

For patients who:

• Have not responded to hyaluronic acid or corticosteroids.
• Want long-term relief from a single injection.
• Prefer a device-like solution rather than multiple regenerative injections.

2. As an Adjunct to Orthobiologics

This is where Arthrosamid® shines in a regenerative practice.

• PRP (Platelet-Rich Plasma): Delivers growth factors that reduce inflammation and stimulate healing【Meheux et al., 2016】【Belk et al., 2021】.
• Stem Cells (MSCs): May modulate inflammation and promote repair【Chahla et al., 2021】.
• Arthrosamid®: Provides a mechanical cushion and reduces synovial irritation.

👉 Used together, biologics target biology, while Arthrosamid® stabilises mechanics. This dual approach supports both healing and long-lasting comfort.

3. As a Bridge to Surgery

For patients nearing knee replacement but not ready to proceed, Arthrosamid® can:

• Maintain mobility.
• Control pain while waiting for surgery.
• Delay surgical intervention without leaving patients untreated.

Who May Benefit Most?

• Patients with synovitis-driven OA (inflammation of the lining seen on ultrasound or MRI).
• Those seeking a longer-lasting injection option.
• Individuals who want a complement to PRP or MSCs for layered benefit.
• Patients not yet ready for joint replacement but struggling with daily pain.

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Practical Takeaways for Patients

• Procedure: Single injection under ultrasound, with local anaesthetic and antibiotics.
• Recovery: Expect mild soreness or swelling; avoid strenuous activity for a few weeks.
• Onset: Relief often begins within weeks; maximum benefit by 3 months.
• Durability: Relief may last up to 4 years from a single injection.
• Role: Works alone, in combination with PRP/orthobiologics, or as a bridge before surgery.

Conclusion

Arthrosamid® represents a new dimension in knee osteoarthritis care. By integrating with the synovium, it directly addresses pain from synovitis, while providing structural cushioning.

It is not an “either-or” choice against orthobiologics or surgery. Instead, it is a versatile option:

• Alone for durable relief.
• With PRP or MSCs for combined biological and mechanical benefit.
• Before surgery as a bridge.

In this way, Arthrosamid® helps close the treatment gap between conservative care and joint replacement, giving patients more personalised, layered, and lasting solutions for their osteoarthritis journey.

References

• Scanzello CR, Goldring SR. Arthritis Res Ther. 2012.
• Hill CL et al. Arthritis Rheum. 2007.
• Tetsworth K et al. Osteoarthritis Cartilage. 2018.
• Larsen NE et al. Knee Surg Sports Traumatol Arthrosc. 2021.
• Bannuru RR et al. Ann Intern Med. 2019.
• Meheux CJ et al. Am J Sports Med. 2016.
• Belk JW et al. Arthroscopy. 2021.
• Chahla J et al. Am J Sports Med. 2021.