Questions people ask about sore joints

Sources

1. FDA's consumer alert states verbatim of stem cell products, exosome products, adipose-derived stromal vascular fraction, umbilical cord blood, Wharton's Jelly and amniotic fluid products: "None of these products have been approved for the treatment of any orthopedic condition, such as osteoarthritis, tendonitis, disc disease, tennis elbow, back pain, hip pain, knee pain, neck pain, or shoulder pain." The only stem cell products carrying FDA licensure are blood-forming cells derived from umbilical cord blood, licensed only for disorders of blood production, and there are currently no licensed exosome products.

   U.S. Food and Drug Administration — Consumer Alert on Regenerative Medicine Products Including Stem Cells and Exosomes. FDA, Consumers (Biologics), 2020.

2. A meta-analysis of seven comparative studies (four randomised, 234 patients) of PRP added to microfracture found statistically significant improvements in knees at 12 and 24 months and in ankles at 12 months - but the improvement did NOT reach the minimal clinically important difference, meaning patients would not have perceived it. Overall evidence was graded low.

   Boffa A, et al. — Platelet-Rich Plasma Augmentation to Microfracture Provides a Limited Benefit for the Treatment of Cartilage Lesions: A Meta-analysis.. Orthop J Sports Med, 2020. DOI: 10.1177/2325967120910504.

3. A 2026 meta-analysis of 11 comparative studies (6 randomised trials, 664 patients) reached a more favourable conclusion, reporting that PRP plus microfracture improved VAS at 3, 12 and 24 months, IKDC at 24 months and Lysholm at every time point versus microfracture alone. Set against the 2020 meta-analysis finding a sub-threshold benefit, the honest summary is that this question is unsettled, not settled in either direction.

   Mahamat Abdramane A, et al. — Effectiveness of platelet-rich plasma plus microfracture compared with microfracture alone in the treatment of knee cartilage lesions: a systematic review and meta-analysis of comparative studies.. Int J Surg, 2026. DOI: 10.1097/JS9.0000000000004610.

4. In the RESTORE randomised trial, 288 people aged 50 or over with symptomatic mild-to-moderate medial knee osteoarthritis received three weekly injections of leukocyte-poor PRP or saline placebo. At 12 months there was no significant difference in knee pain (-2.1 versus -1.8 points) and none in medial tibial cartilage VOLUME (-1.4% versus -1.2%). Twenty-nine of 31 prespecified secondary outcomes also showed no difference.

   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.

5. A four-arm phase 2/3 randomised trial assigned 480 patients with knee osteoarthritis to autologous bone marrow aspirate concentrate, allogeneic umbilical cord tissue mesenchymal stromal cells, autologous adipose stromal vascular fraction or a corticosteroid injection. At one year, no cell injection was superior to another or to the corticosteroid control, and NONE of the four groups showed a significant change in the MRI osteoarthritis score from baseline.

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

6. In a meta-analysis of 63 studies covering 5,397 knees of 4,751 adults with NO symptoms and no injury, the pooled prevalence of cartilage defects on MRI was 24% (95% CI 15% to 34%), rising from 11% in adults under 40 to 43% in adults aged 40 and over. Meniscal tears were present in 10%, bone marrow lesions in 18% and osteophytes in 25%.

   Culvenor AG, et al. — Prevalence of knee osteoarthritis features on magnetic resonance imaging in asymptomatic uninjured adults: a systematic review and meta-analysis.. Br J Sports Med, 2019. DOI: 10.1136/bjsports-2018-099257.

7. A JBJS evidence-based review of chondral lesions of the knee sets management by lesion size, location, limb alignment and rotation, and patient demand rather than by product: osteochondral autograft transfer is described as durable and predictable for smaller lesions (under 2 cm2) in young active patients, while lesions of 2 cm2 or more are typically treated with osteochondral allograft transplantation, particulated juvenile articular cartilage, or matrix-associated chondrocyte implantation, with favourable mid- and long-term results reported for allograft or MACI in large lesions of 3 cm2 or more.

   Dekker TJ, et al. — Chondral Lesions of the Knee: An Evidence-Based Approach.. J Bone Joint Surg Am, 2021. DOI: 10.2106/JBJS.20.01161.

8. FDA biologics licence BL 125603 (Vericel) describes MACI verbatim as "an autologous cellularized scaffold product indicated for the repair of symptomatic, single or multiple full-thickness cartilage defects of the knee with or without bone involvement in adults." The licensed indication is a two-stage surgical implantation for full-thickness DEFECTS of the knee in adults. It is not an injection, it is not licensed for osteoarthritis, and it is not licensed for any joint other than the knee.

   U.S. Food and Drug Administration — MACI (autologous cultured chondrocytes on porcine collagen membrane). FDA, Center for Biologics Evaluation and Research, 2024.