Patient guide
Steroid, gel or PRP? What the evidence says about knee injections.
Injections are sometimes used for knee osteoarthritis (wear-and-tear arthritis). Here is what the research shows for each one, in plain words, so you can talk it through with your doctor.
First things first
Injections are add-ons, not the starting point.
Guidelines put education, exercise and, if needed, weight loss first for everyone with knee osteoarthritis. Injections are added to these for some people [1,4]. Results vary from person to person.
At a glance
How the injections compare
| Injection | Who it may help | How long it may last | Strength of evidence | Main caution |
|---|---|---|---|---|
| Steroid | A painful flare, when other medicines haven’t worked or aren’t suitable [1] | A few weeks; NICE says 2 to 10 weeks [1,5] | Moderate [3] | Repeated injections may speed up cartilage loss [3,6] |
| Hyaluronic acid (gel) | Some people who can’t take anti-inflammatory tablets, or still have pain despite them [7] | Possibly beyond 12 weeks [4]; one injection alone did no better than placebo (a dummy injection) [7] | Strong evidence that the benefit is tiny [8] | The benefit is usually too small to notice; NICE advises against it [1,8] |
| PRP | Mild to moderate arthritis, age 80 or under, after other treatments haven’t helped [9] | Against saline: better at 3 and 6 months, not at 12; importance unclear [10,11] | Limited, conflicting [3] | Not standardised; guidelines disagree [2,3,4] |
| Stem-cell / BMAC | Not established for knee arthritis [12] | No benefit shown over a steroid injection or saline that patients would notice [12,13] | Weak, insufficient [12] | Guidelines advise against it or limit it to research [1,2,4] |
01 · Steroid
Steroid (corticosteroid) injection
- Who it may help
- People with a painful flare of knee osteoarthritis, when other medicines haven’t worked or aren’t suitable, or to make exercise possible [1].
- How long it lasts
- Short-term relief. NICE puts it at 2 to 10 weeks [1]. A 2024 review found a meaningful benefit over placebo only up to about 6 weeks, and no difference at 6 months or more [5].
- How strong the evidence is
- Moderate, according to the American Academy of Orthopaedic Surgeons (AAOS) [3].
- Cautions
- In a 2-year trial, a steroid injection every 3 months caused more cartilage loss than saline (salt-water) injections and gave no better pain relief [6]. AAOS notes that injections may speed up osteoarthritis [3].
02 · Gel
Hyaluronic acid (“gel” or viscosupplement)
- Who it may help
- Some people who can’t take anti-inflammatory tablets, or are still in pain despite them, given once a flare has settled [7].
- How long it lasts
- One guideline notes benefit beyond 12 weeks [4]. A single injection gave no benefit over placebo, while a course of several injections did better [7].
- How strong the evidence is
- A large review of 169 trials (21,163 people) found strong evidence that the pain benefit over placebo is tiny: 2 mm on a 100 mm pain scale, below what patients notice [8].
- Cautions
- The same review found more serious side effects than with placebo [8]. NICE (UK) advises not offering it, and AAOS does not recommend it for routine use [1,3]. Other guidelines give it weak or conditional support [4,7], so the evidence is mixed.
03 · PRP
PRP (platelet-rich plasma)
PRP is prepared from your own blood and injected into the knee.
- Who it may help
- PRP is not right for everyone. An expert consensus considers it for people aged 80 or under with mild to moderate arthritis, after other treatments or injections haven’t helped. It is not considered a first treatment, or suitable for severe (“bone on bone”) arthritis [9].
- How long it lasts
- Compared with saline, pain was better at 3 and 6 months but not at 12 months, and the authors call the benefit’s importance “debatable” [10]. In a large trial of 288 people aged 50 and over, where neither patients nor doctors knew who got PRP, three PRP injections were no better than saline at 12 months, for pain or for cartilage [11].
- How strong the evidence is
- Limited, and the results conflict [3]. AAOS says it “may reduce pain and improve function”, with limited evidence [3].
- Cautions
- PRP is not standardised: kits, platelet dose and white-cell content differ, so it is hard to know exactly what is being injected [2,4]. More studies reported local soreness and injection pain with PRP than with hyaluronic acid [3]. Guidelines disagree: the American College of Rheumatology and the Osteoarthritis Research Society International (OARSI) advise against it [2,4], while AAOS gives limited support [3].
A short note
Stem-cell and BMAC injections
You may see stem-cell or BMAC (bone marrow aspirate concentrate) injections advertised for knee arthritis. The evidence for them is weak: an AAOS review found it insufficient to show benefit [12], and in the largest trial they did no better than a steroid injection at 12 months [13]. Guidelines from NICE (UK), the American College of Rheumatology (US) and OARSI advise against them or limit them to research [1,2,4]. In India, the Indian Council of Medical Research (ICMR) says stem-cell therapy should not be offered as a standard or routine treatment for bone and joint conditions [14]. Dr Aggarwal does use bone marrow concentrate (BMAC) in selected cases, for example alongside hip core decompression. For knee arthritis, the evidence is still limited, and NICE and ACR advise against routine use [1,2].
Talking it through
Questions to ask before any injection
- Which injection, and why for my knee?
- How long might it help, and what is the plan if it doesn’t?
- What are the side effects?
- For PRP: which kit, how much blood is taken, and how many injections?
At Aggarwal Clinic, injections are considered case by case after an examination, and discussed with you. Your doctor will discuss whether one suits you.
Sources
References
- National Institute for Health and Care Excellence. Osteoarthritis in over 16s: diagnosis and management (NG226). NICE; 2022. nice.org.uk/guidance/ng226
- Kolasinski SL, et al. 2019 American College of Rheumatology/Arthritis Foundation guideline for the management of osteoarthritis of the hand, hip, and knee. Arthritis Care Res. 2020;72(2):149-162. doi:10.1002/acr.24131
- Brophy RH, Fillingham YA. AAOS clinical practice guideline summary: management of osteoarthritis of the knee (nonarthroplasty), 3rd ed. J Am Acad Orthop Surg. 2022;30(9):e721-e729. doi:10.5435/JAAOS-D-21-01233
- Bannuru RR, et al. OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis. Osteoarthritis Cartilage. 2019;27(11):1578-1589. doi:10.1016/j.joca.2019.06.011
- Bensa A, et al. Intra-articular corticosteroid injections provide a clinically relevant benefit compared to placebo only at short-term follow-up in patients with knee osteoarthritis. Knee Surg Sports Traumatol Arthrosc. 2024;32(2):311-322. doi:10.1002/ksa.12057
- McAlindon TE, et al. Effect of intra-articular triamcinolone vs saline on knee cartilage volume and pain in patients with knee osteoarthritis: a randomized clinical trial. JAMA. 2017;317(19):1967-1975. doi:10.1001/jama.2017.5283
- Bruyère O, et al. An updated algorithm recommendation for the management of knee osteoarthritis (ESCEO). Semin Arthritis Rheum. 2019;49(3):337-350. doi:10.1016/j.semarthrit.2019.04.008
- Pereira TV, et al. Viscosupplementation for knee osteoarthritis: systematic review and meta-analysis. BMJ. 2022;378:e069722. doi:10.1136/bmj-2022-069722
- Kon E, et al. Platelet-rich plasma injections for the management of knee osteoarthritis: the ESSKA-ICRS consensus. Knee Surg Sports Traumatol Arthrosc. 2024;32(11):2938-2949. doi:10.1002/ksa.12320
- Auroux M, et al. Efficacy of intra-articular platelet-rich plasma compared with placebo in knee osteoarthritis: a systematic review and meta-analysis. Joint Bone Spine. 2025;92(6):105947. doi:10.1016/j.jbspin.2025.105947
- Bennell KL, et al. Effect of intra-articular platelet-rich plasma vs placebo injection on pain and medial tibial cartilage volume in patients with knee osteoarthritis: the RESTORE randomized clinical trial. JAMA. 2021;326(20):2021-2030. doi:10.1001/jama.2021.19415
- Aneja A, et al. AAOS technology overview summary: concentrated bone marrow aspirate for knee osteoarthritis. J Am Acad Orthop Surg. 2023;31(1):e9-e13. doi:10.5435/JAAOS-D-22-00228
- Mautner K, et al. Cell-based versus corticosteroid injections for knee pain in osteoarthritis: a randomized phase 3 trial. Nat Med. 2023;29(12):3120-3126. doi:10.1038/s41591-023-02632-w
- Indian Council of Medical Research. Evidence based status of stem cell therapy for human diseases. ICMR; 2021. Section 1, Orthopedic conditions/injuries.
Evidence checked 4 October 2026.
General information only; it doesn’t replace a consultation. In an emergency, call 112.