Osteoarthritis of the knee is one of the most common causes of joint pain and stiffness in adults. In the UK, around 5 million people are believed to suffer from arthritis, and 1 in 5 people over the age of 40 will develop osteoarthritis of the knee. For many, it’s a gradual process, a little stiffness after walking, an ache when climbing stairs that can slowly progress into chronic pain and limited mobility.
While exercise, physiotherapy and weight management remain the cornerstones of care, injections for knee arthritis can play a crucial role in managing pain and improving function. From corticosteroid injections to newer therapies like Arthrosamid, there are several options that can help depending on your symptoms, lifestyle and goals.
Understanding Osteoarthritis of the Knee
The knee joint is formed where the thigh bone (femur) meets the shin bone (tibia), and the kneecap (patella) slides over the front. The ends of these bones are covered with articular cartilage, a smooth, water and hyaluronic acid rich tissue that absorbs shock and allows frictionless movement.
How Cartilage Degenerates
Articular cartilage is partly made of water and hyaluronic acid and stays healthy through loading and movement.
- Too little load (sedentary lifestyle) can cause cartilage to weaken.
- Too much load (repetitive stress or heavy impact) can accelerate wear.
Cartilage wear is graded from 0 to 4 — grade 0 being normal, and grade 4 representing full cartilage loss with exposed bone. Most injections work for mild to moderate arthritis, however anecdotally they can also have a positive effect in more advanced arthritis.
Other Joint Changes
The meniscus – a C-shaped pad of cartilage – acts as extra shock absorbers. With age or injury, it can tear, degenerate, or extrude, reducing the knee’s ability to handle load. The synovial membrane, which lines the joint and produces lubricating fluid, can become thinned and disregulated as well as inflamed causing a synovitis and contributes to swelling. Bone spurs called osteophytes can also develop around the edge of the joint visible on X-ray, MRI or ultrasound.
Why Arthritis Develops
Arthritis results from multiple factors, including genetics, age, trauma and lifestyle.
- Trauma and sports injuries: Meniscal tears or knee surgery such as meniscal repairs and ACL reconstruction increase the risk of developing osteoarthritis later in life.
- Body weight: Excess weight increases mechanical load but also triggers inflammation, since body fat is metabolically active and releases inflammatory cytokines that can lead to cartilage wear.
- Lifestyle: Overuse, poor muscle strength, or inactivity can all alter knee mechanics and accelerate wear.
Reducing Inflammation Naturally
Because inflammation plays such a key role in osteoarthritis, managing it can significantly reduce symptoms. A healthy diet and supplements such as omega-3 fish oil and turmeric (curcumin) may offer mild anti-inflammatory benefits. Longer-term use of chondroitin and glucosamine sulfate has shown modest evidence in reducing pain in some people with knee osteoarthritis and may be a useful addition for some.
Emerging medications such as GLP-1 agonists (e.g. Mounjaro), primarily used for weight loss, also appear to have anti-inflammatory properties reducing both mechanical and metabolic stress on the knee.
The Role of Physiotherapy and Load Management
Beyond conventional physiotherapy including manual therapy and exercise rehabilitation, physiotherapists in the U.K. can also perform injections. In fact injections for knee arthritis work best when combined with targeted physiotherapy. The goal is to load, not overload the joint.
- Complete rest weakens muscles and worsens cartilage health.
- Controlled loading through swimming, cycling, walking, and strength training maintains hydration and resilience of the cartilage.
- Strengthening the quads, hamstrings, calves, and glutes helps dissipate force and protect the knee joint.
Muscle acts as a natural shock absorber and a critical ally in any osteoarthritis treatment plan.
Types of Injections for Knee Arthritis
Injection therapy can reduce pain, control inflammation, and restore joint lubrication. Below are the main types of injections for knee arthritis, how they work, and how long their benefits typically last.
1. Corticosteroid Injections
Corticosteroids (commonly called steroid injections) are the most frequently used injections for knee arthritis. They work by suppressing inflammation in the synovial lining.
- Onset: Takes a few days to work.
- Duration: Relief typically lasts 4–6 weeks, sometimes up to 3 months.
- Effectiveness: Particularly helpful for acutely swollen, painful knees.
Risks and Precautions
Repeated steroid injections can be chondrotoxic (damaging to cartilage) and often provide diminishing benefit over time.
Contraindications include:
- Pregnancy
- Poorly controlled diabetes
- Use of blood thinners
- Active infection or recent vaccination
- Current antibiotic use
Risks (though rare) include infection, skin depigmentation, fat atrophy, and tendon rupture.
2. Hyaluronic Acid (Viscosupplementation)
Hyaluronic acid (HA) occurs naturally in synovial fluid, giving it viscosity and shock-absorbing properties. In OA, levels decline, making movement painful. Injecting HA restores lubrication.
- Onset: May take several weeks to feel improvement.
- Duration: Lasts 6–12 months depending on product type.
- Effectiveness: Around 75–80% of patients report benefit.
Types of Hyaluronic Acid
- Low molecular weight HA (e.g. Ostenil Plus) may act more in an anti-inflammatory capacity and as a lubricant – good for younger, post-surgical athletes.
- High molecular weight HA (e.g. Duralane) may reside in the joint longer and provide more cushioning – suited to older patients with moderate wear.
- Some products combine both low and high molecular weight HA (Synovial) or even blend steroid with HA (e.g. Cyngal), for enhanced short- and long-term relief.
What determines your choice of HA injection will be a decision based on pain, swelling, lubrication, cushioning and can be decided in conjunction with your injection therapist.
3. Platelet-Rich Plasma (PRP)
PRP therapy involves drawing a small amount of blood, spinning it in a centrifuge, and re-injecting the plasma rich in platelets and growth factors. These factors may help reduce inflammation and support tissue repair.
- Duration: Relief can last up to 12 months in some patients.
- Evidence: Mixed; results vary based on preparation (leukocyte-rich vs. poor) and injection frequency.
- Best suited for: Active individuals with early-to-moderate osteoarthritis seeking a regenerative option.
4. Arthrosamid (Polyacrylamide Hydrogel Injection)
Arthrosamid® is one of the newest and most innovative injections for knee arthritis. Originally used in veterinary medicine, it’s now available for human use with strong clinical outcomes.
This hydrogel implant is 97.5% water and 2.5% polyacrylamide. Once injected (6ml), it integrates with the synovial lining, creating a soft, cushioning scaffold that helps the synovium self-regulate and calm inflammation.
- Onset: Gradual improvement over several months.
- Duration: Clinical studies show results lasting 3–5 years or more.
- Advantages: Non-biodegradable, non-migratory, and long-lasting.
- Best for: Painful, swollen knees with synovitis or effusion.
5. Cost and Considerations
Private injection therapy costs vary by product and clinic:
- Steroid injection: £200–£300
- Hyaluronic acid: £300–£400
- PRP: £500+
- Arthrosamid®: £2,500–£3,500
While costlier, Arthrosamid may provide several years of relief, making it a strong long-term investment for suitable candidates.
Choosing the Right Injection for You
The best injection for knee arthritis depends on your:
- Age and activity level
- Degree of cartilage wear (OA grade)
- Presence of swelling or inflammation
- Previous surgery or injury
- Treatment goals and budget
A comprehensive assessment, often including ultrasound imaging, helps determine the best approach. Injections are most effective when combined with ongoing physiotherapy, exercise, and weight management.
Key Takeaways
- Knee osteoarthritis affects millions and is influenced by injury, inflammation, and lifestyle.
- Injections can reduce pain, control inflammation, and restore mobility when tailored to the individual.
- Steroids provide fast relief but short duration.
- Hyaluronic acid restores lubrication for up to a year.
- PRP offers regenerative potential.
- Arthrosamid® delivers long-lasting cushioning and symptom relief — up to 5 years.
- Combined with exercise, strength training, and weight management, injection therapy can help keep you active and independent.
If you’re considering injections for knee arthritis, book a consultation with your physiotherapist at Wandsworth Physiotherapy. We have clinics in Wandsworth Town, Clapham Junction and Battersea Nine Elms and can comprehensively assess and ultrasound scan your knee. We can design a tailored plan combining the right injection, targeted rehabilitation and lifestyle support can make a remarkable difference in knee health and quality of life.