Injections Explained — Cortisone, Hyaluronic Acid and PRP

Part of The Joint Replacement Guide — Phase 2: Considering Surgery · Article 7 of 44 · Hip & Knee

Key Points

A joint injection may provide temporary symptom relief for some people, but it does not cure osteoarthritis or reverse established structural changes.
NICE advises considering a corticosteroid injection when other suitable medicines have not helped or cannot be used, or when short-term relief may help someone participate in therapeutic exercise.
NICE describes the expected benefit from a corticosteroid injection as short term—typically around 2 to 10 weeks—although individual responses vary.
NICE advises that hyaluronan injections should not be offered to manage osteoarthritis.
For knee osteoarthritis, NICE considers the evidence for platelet-rich plasma, or PRP, to be limited in quality. It should only be used with special arrangements for governance, informed consent, and audit or research.
Injections given close to hip or knee replacement have been associated with a higher risk of infection in some observational studies. Many surgical units avoid operating within three months of an injection, but local policies differ.
All injections have potential risks. The expected benefit, alternatives, cost and possible adverse effects should be discussed before consent.

Corticosteroid Injections

Corticosteroids are anti-inflammatory medicines. When injected into a joint, they may temporarily reduce inflammation and pain.

NICE advises considering an intra-articular corticosteroid injection when:

other suitable medicines have been ineffective or are unsuitable; or
short-term pain relief may help someone participate in therapeutic exercise.[1]

The injection does not repair cartilage or alter the long-term course of osteoarthritis. NICE advises explaining that any benefit is expected to be short term, generally around 2 to 10 weeks.[1] Some people experience useful relief, some experience little or no benefit, and symptoms may return.

Evidence is less consistent for hip osteoarthritis than for knee osteoarthritis. Hip injections also usually require image guidance to place the needle accurately within the joint. The responsible clinician can explain whether an injection is appropriate and how it would be performed.

Possible Risks of Corticosteroid Injections

Most injections do not cause a serious complication, but no injection is risk-free. Possible adverse effects include:

temporary worsening of pain after the injection
bruising or bleeding
infection
temporary facial flushing
a temporary rise in blood glucose, particularly in people with diabetes
changes in skin colour
thinning of fat or other tissue around the injection site
an allergic reaction
failure to improve symptoms

Medicines that affect bleeding, diabetes, current infection, allergies and other medical conditions may influence whether an injection is appropriate. Do not stop prescribed anticoagulant or antiplatelet medication unless the clinician responsible for it tells you to do so.

Seek urgent medical advice if the joint becomes increasingly painful, hot or markedly swollen after an injection, particularly if you also develop fever, shivering or feel generally unwell. These symptoms could indicate infection and require prompt assessment.[3]

Repeated Corticosteroid Injections

Repeated injections are not a long-term substitute for exercise, weight management where relevant, and other appropriate treatment.

There is no single maximum number or interval that is suitable for every person. Decisions should consider:

how much benefit the previous injection provided
how long the benefit lasted
the joint being treated
other medical conditions
potential cumulative risks
whether joint replacement is being considered

Research has raised concern that frequent repeated corticosteroid injections could adversely affect cartilage or other joint tissues. The size and clinical importance of this risk remain uncertain. It would therefore be inappropriate to promise that repeated injections are harmless or to use them automatically at fixed intervals.

Hyaluronic Acid Injections

Hyaluronic acid, also called hyaluronan, is a natural component of joint fluid. Injecting a manufactured form into a joint is sometimes called viscosupplementation.

Although some studies have reported symptom improvement, the overall evidence is inconsistent and any average benefit appears small. A large systematic review of knee osteoarthritis found that the difference in pain compared with placebo was below the threshold regarded as clinically important.[4]

NICE states:

Do not offer intra-articular hyaluronan injections to manage osteoarthritis.[1]

These injections may still be advertised or provided privately. Availability in private practice does not establish that a treatment is effective, suitable or recommended by NICE.

Anyone considering private treatment should ask about:

the evidence for the particular product
the realistic size and duration of benefit
possible adverse effects
the practitioner’s qualifications
the total cost, including repeat treatment
what follow-up or support is available
whether treatment could affect the timing of future surgery

Platelet-Rich Plasma

PRP is prepared from a sample of the patient’s own blood. The blood is processed to produce plasma containing a higher concentration of platelets, which is then injected into the joint.

Platelets release substances involved in healing and inflammation. However, this biological rationale does not prove that PRP can regrow cartilage or reverse osteoarthritis. PRP should not be described as regenerative treatment with a guaranteed structural benefit.

Some studies of knee osteoarthritis have reported improvements in pain or function, but results are difficult to interpret because:

preparation methods differ
platelet concentrations vary
some preparations contain more white blood cells than others
the number and timing of injections vary
comparison treatments differ
studies vary in quality and duration

NICE states that PRP for knee osteoarthritis raises no major safety concerns, but the evidence for efficacy is limited in quality. NICE therefore advises that it should only be used with special arrangements for clinical governance, consent, and audit or research.[2]

This guidance relates specifically to knee osteoarthritis. Evidence and recommendations should not automatically be assumed to apply to hip osteoarthritis.

PRP is not routinely available for osteoarthritis throughout the NHS. Local funding and provision vary. If it is offered privately, the patient should receive clear information about the uncertainty, costs, alternatives and arrangements if complications occur.

Injections Before Joint Replacement

Some observational studies report a higher rate of infection after hip or knee replacement when an intra-articular injection was given close to surgery, particularly within the preceding three months.[5,6]

These studies show an association. They cannot establish with certainty that the injection caused the infection, and the estimated risk varies between studies. Nevertheless, infection around a joint replacement is a serious complication, so many surgical units use a precautionary interval.

If joint replacement is being considered:

tell the injecting clinician before proceeding;
tell the surgical team the date, joint and type of every recent injection;
ask how long the operating unit requires between an injection and surgery;
do not assume that all injection types or hospitals follow the same policy.

A three-month interval is commonly used, but the treating surgical team’s policy should take precedence. Having had a recent injection does not mean that infection will occur; it may mean that elective surgery needs to be scheduled later.

What an Injection Can and Cannot Do

An injection may sometimes be used to:

provide short-term symptom relief
support participation in exercise or rehabilitation
help manage a temporary increase in symptoms
provide an option when some medicines are ineffective or unsuitable

An injection cannot be guaranteed to:

relieve pain
restore damaged cartilage
stop osteoarthritis progressing
prevent or indefinitely delay joint replacement

The decision should take account of expected benefit, uncertainty, possible risks, alternative treatments, cost and the person’s priorities.

Important Information

This article provides general educational information and does not replace individual clinical advice or the consent discussion required before a procedure.

An injection should only be performed by an appropriately trained healthcare professional using suitable infection-control procedures. The clinician should confirm the intended joint, medicine or product, expected benefits, material risks, alternatives and aftercare before proceeding.

Seek urgent medical advice after an injection if you develop increasing pain, marked swelling, heat or skin-colour change around the joint, fever, shivering or a general feeling of being unwell.

References

National Institute for Health and Care Excellence. Osteoarthritis in over 16s: diagnosis and management. NICE guideline NG226. Published 19 October 2022. Available from: https://www.nice.org.uk/guidance/ng226 [Accessed 14 August 2026].
National Institute for Health and Care Excellence. Platelet-rich plasma injections for knee osteoarthritis. NICE HealthTech guidance HTG497. Published 23 January 2019; migrated to HealthTech guidance January 2026. Available from: https://www.nice.org.uk/guidance/htg497 [Accessed 14 August 2026].
Guy’s and St Thomas’ NHS Foundation Trust. Steroid injections for joint and tendon pain: risks and side effects. Available from: https://www.guysandstthomas.nhs.uk/health-information/steroid-injections-joint-and-tendon-pain [Accessed 14 August 2026].
Pereira TV, Jüni P, Saadat P, Xing D, Yao L, Bobos P, et al. Viscosupplementation for knee osteoarthritis: systematic review and meta-analysis. BMJ. 2022;378. doi: https://doi.org/10.1136/bmj-2022-069722
Kim YM, Joo YB, Song JH. Preoperative intra-articular steroid injections within 3 months increase the risk of periprosthetic joint infection in total knee arthroplasty: a systematic review and meta-analysis. J Orthop Surg Res. 2023;18:148. doi: https://doi.org/10.1186/s13018-023-03637-4
Saracco M, Ciriello V, D’Angelo F, Zagra L, Solarino G, Logroscino G. Do prior intra-articular injections impact on the risk of periprosthetic joint infection in patients undergoing total hip arthroplasty? A meta-analysis with a focus on the timing of injection before surgery. EFORT Open Rev. 2023;8(6):459–467. doi: https://doi.org/10.1530/EOR-23-0028

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