Q1: Do injections cure osteoarthritis?
A: No. Injections manage symptoms — they don’t repair cartilage or reverse OA. Exercise and weight management remain the most effective long-term treatments.
Q2: How long does cortisone last for knee OA?
A: Most people get two to six weeks of relief. Repeated long-term use may accelerate cartilage loss.
Q3: Is hyaluronic acid better than cortisone?
A: Evidence is mixed. Some people benefit, others don’t. It’s generally considered safe and may suit those who can’t tolerate NSAIDs.
Q4: What is PRP and does it work for OA?
A: PRP uses your own blood to create a growth-factor-rich injection. Emerging evidence is positive but it’s not yet covered by Medicare.
Q5: What’s the most evidence-based treatment for knee OA?
A: Progressive exercise and weight management — consistently the highest-ranked treatments in clinical guidelines worldwide.
Injections for Knee and Hip Osteoarthritis: The Evidence You Need to Make a Smart Decision
If you’re living with knee or hip osteoarthritis (OA), you’ve probably been offered — or asked about — injections at some point. Cortisone, hyaluronic acid, PRP — the choices can feel overwhelming, and the information online is often confusing or commercially motivated.
At Arana Hills Physiotherapy, we believe in giving people clear, evidence-based information so they can make decisions that are right for their situation. Here’s what the research actually says about each type of injection for OA
Understanding Osteoarthritis: It’s More Than Just ‘Wear and Tear’
OA is often described as cartilage wearing down — and that’s partly true. But the picture is much more complex. OA involves changes in bone, synovial tissue (the joint lining), muscles, and the nervous system. Pain in OA doesn’t correlate neatly with cartilage damage on a scan — some people with severe X-ray changes have minimal pain, while others with mild imaging findings are in significant discomfort.
This complexity is why OA management needs to be multidimensional — and why no single injection is going to be the complete answer. That said, injections can play a valuable role as part of a broader plan
Cortisone Injections for Knee and Hip OA: Short-Term Help, Long-Term Caution
Cortisone (corticosteroid) injections reduce inflammation inside the joint and typically provide pain relief within a few days. For many people, this window — usually two to six weeks — is genuinely useful for improving function and allowing exercise to begin.
However, the long-term picture is more concerning. A landmark 2017 randomised controlled trial published in JAMA found that patients receiving cortisone injections every three months for two years experienced greater cartilage loss than those receiving a placebo — a finding that changed prescribing habits significantly. Current Australian and international guidelines recommend limiting cortisone injections to no more than three to four per year in any single joint, and ideally using them as a bridge to active rehabilitation rather than as ongoing symptom management.
Cortisone injections are best used strategically — for example, before starting a physiotherapy program when pain is too severe to exercise, or ahead of a specific event. They’re not a maintenance strategy
Hyaluronic Acid Injections: The Evidence Is Mixed, But Some People Benefit
Hyaluronic acid (viscosupplementation) is a substance that mimics the natural lubricating fluid in your joints. It’s been used for knee OA for decades. The evidence, however, is genuinely mixed. Some large meta-analyses show a small but significant benefit over placebo; others, including a well-cited Cochrane Review, conclude that the benefit is not clinically meaningful when accounting for publication bias and placebo effect.
Where hyaluronic acid may be most useful is for people with mild to moderate knee OA who haven’t responded well to cortisone, who have contraindications to NSAIDs, or who want to avoid cortisone’s cartilage effects. The safety profile is good — adverse events are uncommon. It’s generally not covered by Medicare and costs $300–600 per injection course.
It’s worth noting that the evidence is stronger for knee OA than hip OA, where results have been less consistent
PRP Injections: Promising but Still Emerging
Platelet-rich plasma (PRP) involves taking a small amount of your blood, spinning it in a centrifuge to concentrate the platelets and growth factors, and injecting it into the joint. The idea is that these growth factors stimulate healing and reduce inflammation in the joint environment.
The evidence is evolving quickly. A 2022 meta-analysis in the British Journal of Sports Medicine comparing PRP to hyaluronic acid for knee OA found PRP was more effective at 12 months — with a moderate effect size. A 2023 network meta-analysis in the Lancet ranked PRP above both cortisone and hyaluronic acid for short and medium-term pain relief in knee OA, though the quality of evidence was rated as low to moderate.
PRP is not yet covered by Medicare in Australia and typically costs $400–800 per injection. It may be a reasonable option for people who haven’t responded to other treatments and are keen to avoid surgery. The preparation protocol and concentration of platelets varies between providers, which makes comparing results across studies challenging.
Exercise Has the Strongest Evidence for Knee and Hip OA
Exercise. Consistently, across every major clinical guideline — OARSI, NICE, RACGP, and Arthritis Australia — exercise is ranked as the single most effective intervention for osteoarthritis. Specifically, strengthening the quadriceps and hip muscles reduces joint loading, improves pain, and slows functional decline. The benefits are dose-dependent and long-lasting when maintained.
Weight management for people who are overweight is also strongly evidence-based — reducing body weight by just five percent can significantly reduce pain in knee OA. Patient education about OA (understanding what it is and isn’t, and why movement helps rather than hurts) is also consistently associated with better outcomes.
How to Use Injections Wisely as Part of Your OA Plan
The most effective approach combines injections strategically with active rehabilitation. If you’re in enough pain that you can’t exercise, a cortisone injection to get you moving is a legitimate strategy. But the injection should be paired with a physiotherapy program — not used as a standalone treatment.
At Arana Hills Physiotherapy, we build individualised OA management plans that include exercise prescription, education, hands-on treatment, and guidance on when to involve your GP for injection referral. Because OA is a lifelong condition, building sustainable habits matters more than any short-term fix
Ready to feel better? Book with Arana Hills Physiotherapy
Sources & Further Reading
• JAMA: Corticosteroid injections and cartilage loss in knee OA (2017)
• Cochrane Review: Hyaluronic acid for osteoarthritis of the knee
• BJSports Medicine: PRP vs hyaluronic acid for knee OA meta-analysis (2022)
• OARSI Guidelines: Management of knee and hip OA (2019)
• Arthritis Australia: Exercise and OA evidence summary