Injections Explained — Cortisone, Hyaluronic Acid and PRP

Part of The Joint Replacement Guide — Phase 2: Considering Surgery · Article 7 of 42 · Hip & Knee

Key Points

  • Injections can provide useful short-term relief but are not a long-term cure for osteoarthritis.
  • Cortisone (corticosteroid) injections have the best evidence of the three, though relief is typically measured in weeks to a few months.
  • Hyaluronic acid injections have weak, inconsistent evidence and are not routinely recommended.
  • PRP (platelet-rich plasma) is promising in some studies but the evidence base is still developing, and it is not routinely NHS-funded for OA.
  • Injections are generally best avoided in the months immediately before a planned joint replacement, due to a theoretical infection risk.

Corticosteroid (Cortisone) Injections

A corticosteroid injection delivers a concentrated anti-inflammatory medication directly into the joint, aiming to reduce the low-grade inflammation (synovitis) that contributes to OA pain. It is generally the best-evidenced of the three injection types discussed here, and can provide meaningful pain relief — typically lasting somewhere between a few weeks and a few months, though this varies considerably between individuals.

It is not, however, a treatment that changes the underlying course of the disease, and repeated frequent injections are generally avoided. There is ongoing research interest in whether very frequent corticosteroid injections might have a negative effect on cartilage over time, and many surgical units also advise avoiding an injection in the few months before a planned joint replacement, because of a theoretical (and in some studies, measurable) increase in infection risk around the time of surgery. If you are considering surgery and have recently had, or are due, an injection, it’s worth raising the timing explicitly with your surgical team.

Hyaluronic Acid Injections (Viscosupplementation)

Hyaluronic acid is a naturally occurring component of healthy joint fluid, and the theory behind this injection is to supplement the joint’s own lubrication. In practice, the evidence for meaningful benefit is weak and inconsistent — several large reviews of the available trials have found little difference from placebo injections once study quality and bias are properly accounted for. For this reason, current national guidance does not recommend hyaluronic acid injections as a routine NHS treatment for OA, although it remains available in some private practice settings.

Platelet-Rich Plasma (PRP)

PRP involves taking a sample of your own blood, concentrating the platelets (which contain growth factors involved in tissue repair), and injecting this back into the joint. It is a genuinely interesting area of ongoing research, with some individual studies showing promising results, but the overall evidence base remains mixed and inconsistent — partly because different clinics use quite different preparation methods, making it hard to compare results directly between studies. PRP is not routinely funded on the NHS for osteoarthritis and is generally considered an emerging, rather than an established, treatment at this stage.

What This Means for You

Injections can be genuinely useful — to get through a flare-up, to help you through a big event, or to buy time while you work on the non-surgical measures covered in the previous article. What they don’t do is reverse the underlying joint changes, and it’s worth going into any injection with realistic expectations about how long the benefit is likely to last.

In More Depth

The mechanistic rationale for corticosteroids is reasonably well understood — they suppress the cytokine-driven inflammatory response within the synovium, which is thought to be a meaningful contributor to pain in OA even though OA is fundamentally a degenerative rather than inflammatory condition. The research debate around injection frequency and cartilage safety is genuinely unresolved; some studies have raised concern about accelerated joint space narrowing with frequent dosing, while others have not replicated this finding, and it remains an active area of study. For PRP specifically, a major complicating factor in interpreting the evidence is the lack of standardisation — platelet concentration, presence or absence of white blood cells, and preparation technique all vary between commercial systems, meaning “PRP” in one trial may be quite a different product from “PRP” in another.

This article is general information and does not replace individual clinical advice. Please discuss any injection treatment, including timing relative to planned surgery, with your GP or specialist.

Sources

  • NICE guideline NG226 — Osteoarthritis in over 16s: diagnosis and management (2022)
  • Cochrane Database of Systematic Reviews — intra-articular corticosteroid and hyaluronic acid injections for knee osteoarthritis
  • British Orthopaedic Association — guidance on injections and timing before joint replacement
  • National Joint Registry — periprosthetic joint infection risk data

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