Get straight answers about a sore knee

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1. FDA states plainly that no stem cell, exosome, stromal vascular fraction, umbilical cord blood, Wharton's jelly or amniotic-fluid product has been approved for the treatment of ANY orthopedic condition - it names osteoarthritis, tendonitis, disc disease, tennis elbow, back pain, hip pain, knee pain, neck pain and shoulder pain individually. The only FDA-approved stem cell products in the United States are cord-blood-derived blood-forming stem cells for disorders of the hematopoietic system, and there are currently no FDA-approved exosome products.

   US Food and Drug Administration, Center for Biologics Evaluation and Research — Consumer Alert on Regenerative Medicine Products Including Stem Cells and Exosomes. FDA, 2020.

2. The RESTORE trial - a participant-, injector- and assessor-blinded RCT of 288 adults aged 50+ with symptomatic medial knee OA (Kellgren-Lawrence 2-3) - compared three weekly intra-articular PRP injections against saline placebo, with co-primary endpoints of 12-month knee pain and medial tibial cartilage volume on MRI. PRP did not beat placebo on either. It is the single best-designed test of the specific claim that PRP changes joint structure, and it was negative.

   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. DOI: 10.1001/jama.2021.19415.

3. A four-arm, multicentre, single-blind phase 2/3 randomized trial of 480 knee OA patients (KL II-IV) compared autologous bone marrow aspirate concentrate, autologous adipose stromal vascular fraction and allogeneic umbilical-cord-tissue mesenchymal stromal cells against a corticosteroid injection control. At 12 months NONE of the three orthobiologic injections was superior to another, or to the corticosteroid control, and none of the four groups showed a significant change in MRI osteoarthritis score from baseline. No procedure-related serious adverse events occurred.

   Mautner K, et al. — Cell-based versus corticosteroid injections for knee pain in osteoarthritis: a randomized phase 3 trial.. Nature medicine, 2023. DOI: 10.1038/s41591-023-02632-w.

4. A 2026 systematic review and meta-analysis of 28 randomized trials of intra-articular mesenchymal stem cell-based therapies in knee OA found significant improvements in several pain and function measures (delta-VAS MD -1.67; KOOS pain MD 15.37) but NO significant difference in WOMAC, KOOS quality of life or the Lequesne index, and MRI-based WORMS scores were non-significant - indicating no consistent structural benefit. Its own conclusion: these therapies serve a primarily SYMPTOM-modifying rather than STRUCTURE-modifying role, with higher frequencies of local reactions to weigh against the symptomatic benefit.

   Awad G, et al. — Efficacy and safety of intra-articular mesenchymal stem cell-based therapies in knee osteoarthritis: A systematic review and meta-analysis of randomized controlled trials.. Clinical rheumatology, 2026. DOI: 10.1007/s10067-026-08042-w.

5. A cross-sectional study contacted 273 of 317 US centres offering direct-to-consumer stem-cell therapy, posing as a 57-year-old man with knee osteoarthritis. The mean advertised price of a unilateral same-day stem-cell knee injection was $5,156 (SD $2,446), and centres claimed a mean clinical efficacy of 82% (SD 9.6%) - a figure with no support in the published evidence. The gap between the quoted number and the trial data is the single most useful thing a patient can be told before a consultation.

   Piuzzi NS, et al. — The Stem-Cell Market for the Treatment of Knee Osteoarthritis: A Patient Perspective.. The journal of knee surgery, 2018. DOI: 10.1055/s-0037-1604443.

6. The Cochrane review of exercise for knee osteoarthritis found high-quality evidence that land-based therapeutic exercise provides short-term benefit in pain and physical function, sustained for at least 2-6 months after the programme ends, with mild transient soreness the only reported adverse effect across 45 trials. It is the best-evidenced treatment for this condition and it costs nothing per injection.

   Fransen M, et al. — Exercise for osteoarthritis of the knee.. The Cochrane database of systematic reviews, 2015. DOI: 10.1002/14651858.CD004376.pub3.

7. A randomized trial of 90 patients with KL grade 1-3 knee OA found bone marrow aspirate concentrate - the product most often sold as a 'stem cell injection' - was EQUIVALENT to, not better than, PRP through 24 months, with no statistically significant IKDC or WOMAC difference at any time point. Both arms improved from baseline and plateaued at 3 months.

   Anz AW, et al. — Bone Marrow Aspirate Concentrate Is Equivalent to Platelet-Rich Plasma for the Treatment of Knee Osteoarthritis at 2 Years: A Prospective Randomized Trial.. The American journal of sports medicine, 2022. DOI: 10.1177/03635465211072554.

8. FORWARD, the longest disease-modifying osteoarthritis drug trial reported to date, gave intra-articular sprifermin (a recombinant FGF-18) or placebo to knee OA patients and followed 378 of them for 5 years. Sprifermin produced a significant, sustained dose-response INCREASE in total femorotibial cartilage thickness versus placebo - and WOMAC pain improved about 50% from baseline in ALL groups, including placebo. It is the cleanest demonstration in the literature that adding measurable cartilage and relieving pain are two different results, and that one does not deliver the other.

   Eckstein F, et al. — Long-term structural and symptomatic effects of intra-articular sprifermin in patients with knee osteoarthritis: 5-year results from the FORWARD study.. Annals of the rheumatic diseases, 2021. DOI: 10.1136/annrheumdis-2020-219181.