Knee osteoarthritis (OA) is a common degenerative joint condition affecting millions of people worldwide. It occurs when the cartilage that cushions the knee joint gradually wears down, leading to pain, stiffness, and reduced mobility. While first-line treatments such as physiotherapy, exercise, weight management, and pain relief medications are the cornerstone of osteoarthritis management, some patients may not experience sufficient relief. This is where injection therapies can play a role.
In this article, we explore three key injection options for knee OA: corticosteroid injections, hyaluronic acid injections, and platelet-rich plasma (PRP) injections. We’ll evaluate their effectiveness, risks, costs, and how they fit into an overall treatment plan.
Are Injections the First-Line Treatment for Knee Osteoarthritis?
Before diving into the different types of injections, it’s important to clarify that injection therapies are not recommended as first-line treatments for knee OA. Leading guidelines, including those from the American College of Rheumatology and Australia’s RACGP, advise against using injections as a primary treatment due to limited and variable long-term evidence.
Instead, injections may be considered when:
- Conservative treatments (e.g., physiotherapy, weight loss, exercise) haven’t provided enough relief.
- Surgery is not yet appropriate or desirable.
- Pain or stiffness is limiting daily function or exercise progression.
Crucially, injection therapy should not be viewed as a stand-alone treatment. Instead, it should complement an ongoing, structured plan that includes physical therapy, strengthening exercises, and lifestyle changes.
1. Corticosteroid Injections: Quick Relief for Inflammation
Corticosteroid injections are one of the oldest and most widely used injection therapies for knee OA. These injections work by reducing inflammation inside the joint, which can temporarily relieve pain and improve mobility.
How Do They Work?
Corticosteroids are typically injected into the joint along with a local anaesthetic to minimise pain during the procedure. The anti-inflammatory effect kicks in quickly, and many patients report a noticeable reduction in pain within a few days.
Duration of Relief:
- Short-term benefit: Typically lasts 5 to 15 weeks.
- Repeat injections are common, but they must be spaced out to minimise potential risks.
Risks and Limitations:
- Repeated use may weaken cartilage or bone over time.
- May not provide lasting benefit with repeated doses.
- Provides symptom relief but does not slow or reverse joint damage.
Due to these concerns, clinicians are increasingly cautious about using corticosteroid injections too frequently.
2. Hyaluronic Acid (HA) Injections: Lubricating the Joint
Hyaluronic acid (HA) is a naturally occurring substance found in joint fluid that helps to cushion and lubricate the joint. In people with osteoarthritis, the concentration and quality of HA decreases, contributing to joint pain and stiffness.
HA injections – also known as viscosupplementation – aim to restore lubrication and improve shock absorption in the knee.
Brand Names:
- Commonly known as Synvisc, Hyalgan, or Durolane
How Is It Administered?
- Given as a series of 3 to 5 weekly injections, though some single-injection products are now available.
Effectiveness:
- Research shows modest improvements in pain and mobility.
- Benefits may take a few weeks to become noticeable.
- Relief can last for several months in some patients.
Considerations:
- Much more expensive than corticosteroids.
- Mixed guidelines: Some countries support HA use, while others do not due to inconsistent outcomes.
- Not usually covered by public health systems or private insurers in Australia.
Hyaluronic acid may be a good option for patients who want a non-steroidal alternative and are willing to pay out-of-pocket.
3. Platelet-Rich Plasma (PRP) Injections: A Promising Biological Approach
Platelet-rich plasma (PRP) is an emerging therapy that uses the patient’s own blood to promote healing and reduce inflammation.
How It Works:
- A small amount of the patient’s blood is drawn and spun in a centrifuge.
- This separates the platelet-rich plasma, which contains high concentrations of growth factors and healing proteins.
- The PRP is then injected into the knee joint.
Mechanism of Action:
PRP is believed to:
- Reduce inflammation
- Stimulate repair of cartilage
- Improve the internal environment of the joint
Effectiveness:
- Studies show better symptom relief compared to corticosteroids and HA injections.
- Peak benefit is seen around 3 to 6 months after the injection, with effects lasting up to 12 months.
- Some trials suggest that multiple injections (e.g., a series of three) may provide better results, although this finding is still debated.
Limitations:
- Not currently recommended in international treatment guidelines.
- Not covered by Medicare or private health funds in Australia.
- Self-funded option, typically around $350 per injection.
Despite these limitations, PRP is considered safe and is gaining popularity, especially among patients looking for more natural or regenerative treatment approaches.
Comparing Injection Therapies for Knee OA
| Injection Type | Duration of Relief | Mechanism | Approximate Cost (AUD) | Coverage |
| Corticosteroids | 5-15 weeks | Anti-inflammatory | ~ $50 – $100 | Often covered |
| Hyaluronic Acid (HA) | 3-6 months | Joint lubrication | ~ $300 – $600 | Often self-funded |
| PRP | 6-12 months | Anti-inflammatory & regenerative | ~ $350 per injection | Self-funded only |
Key Considerations Before Getting Injections
While injection therapies offer symptom relief for some individuals with knee OA, they are not a cure and should not replace exercise-based interventions. Here are some factors to consider:
- Severity of OA: Injections may be less effective in advanced stages of joint degeneration.
- Treatment goals: Are you looking for short-term pain relief or long-term joint health?
- Cost: Some injections are not covered by Medicare or private insurance.
- Preferences and lifestyle: Some people prefer to avoid medications; others are looking to delay or avoid surgery.
Ultimately, choosing the right injection therapy—if any—requires a personalised, evidence-informed approach guided by your healthcare provider.
Are Knee Injections Worth It?
Injection therapies can be valuable tools in managing knee osteoarthritis when conservative treatments aren’t enough. Corticosteroid injections provide quick but short-lived relief. Hyaluronic acid injections may help improve joint lubrication, although results vary. PRP injections are a promising new option with longer-lasting results for some, though further high-quality studies are needed.
Regardless of which option is chosen, injections should always be combined with a broader treatment plan that includes physiotherapy, strength training, and lifestyle changes. Talk to your physiotherapist or healthcare provider about whether an injection might help you get moving again—and keep moving.
Need help managing knee osteoarthritis?
Contact the team at Logan Physio to learn how physiotherapy and movement strategies can be tailored alongside injection therapy for lasting results.
References
Belk JW, Kraeutler MJ, Houck DA, Goodrich JA, Dragoo JL, McCarty EC. Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. The American Journal of Sports Medicine. 2021;49(1):249-260. doi:10.1177/0363546520909397
Filardo, G. et al, PRP Injections for the Treatment of Knee Osteoarthritis: A Meta-Analysis of Randomized Controlled Trials, Cartilage, 2021, Vol.13 (1_suppl), p.364S-375S
Gilat, Ret al. Hyaluronic acid and platelet-rich plasma for the management of knee osteoarthritis, International orthopaedics, 2021, Vol.45 (2), p.345-354
Uslu Guvendi E, Askin A, Guvendi G, Kocyigit H. Comparison of efficiency between corticosteroid and platelet rich plasma injection therapies in patients with knee osteoarthritis. Arch Rheumatology, 2018;33:273-281
Vilchez-Cavazos et al 2019, Comparison of the Clinical Effectiveness of Single Versus Multiple Injections of Platelet-Rich Plasma in the Treatment of Knee Osteoarthritis: A Systematic Review and Meta-analysis, The Orthopaedic Journal of Sports Medicine, 7
