Get plain answers to common shoulder questions

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1. Arnold Caplan, who NAMED mesenchymal stem cells more than 25 years earlier, argued in Stem Cells Translational Medicine that the name should be changed. His stated reason is exactly the marketing problem: because MSCs are called 'stem cells', patients infer they will receive direct medical benefit, imagining the cells will differentiate into regenerating tissue-producing cells - and hundreds of clinics and trials now use human MSCs with very few focusing on the in vitro multipotential capacities the name refers to.

   Caplan AI, et al. — Mesenchymal Stem Cells: Time to Change the Name!. Stem cells translational medicine, 2017. DOI: 10.1002/sctm.17-0051.

2. 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.

3. 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.

4. 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.

5. In the MOON Shoulder prospective cohort of 452 patients with symptomatic, ATRAUMATIC full-thickness rotator cuff tears, physical therapy succeeded in more than 70% of patients at 10 years: only 115 (27.0%) had surgery at any point over the decade. Patient-reported outcomes improved with physical therapy and did NOT decline over 10 years in those who never had surgery. The strongest predictor of early surgery was low patient expectation of physical therapy, not tear anatomy.

   Kuhn JE, et al. — The Predictors of Surgery for Symptomatic, Atraumatic Full-Thickness Rotator Cuff Tears Change Over Time: Ten-Year Outcomes of the MOON Shoulder Prospective Cohort.. J Bone Joint Surg Am, 2024. DOI: 10.2106/JBJS.23.00978.

6. A 2026 meta-analysis of 10 randomized trials (n=591) found PRP and corticosteroid indistinguishable at 3-6 weeks and 3 months, with PRP pulling ahead at 6 months: ASES +10.8 (95% CI 4.71-16.80), Constant-Murley +10.7 (1.21-20.27) and VAS pain -0.8 (-1.45 to -0.18), plus fewer adverse events (RR 0.66, 0.44-0.99). The authors describe the benefit as statistically significant but CLINICALLY MODEST.

   Yuwarungsikul C, et al. — Platelet-rich plasma provides modest but durable functional benefit over corticosteroid for rotator cuff tendinopathy: A systematic review and meta-analysis of randomized controlled trials.. Knee Surg Sports Traumatol Arthrosc, 2026. DOI: 10.1002/ksa.70416.

7. A meta-analysis of nine randomized trials (469 patients) found corticosteroid superior to PRP in the SHORT term on Constant, Simple Shoulder Test and ASES scores, no difference at mid-term, and PRP superior in the LONG term on Simple Shoulder Test and ASES. The authors state explicitly that none of these differences reached the minimal clinically important difference.

   Peng Y, et al. — Comparison of the effects of platelet-rich plasma and corticosteroid injection in rotator cuff disease treatment: a systematic review and meta-analysis.. J Shoulder Elbow Surg, 2023. DOI: 10.1016/j.jse.2023.01.037.

8. FDA states verbatim that stem cell, stromal vascular fraction, umbilical cord blood, Wharton's jelly, amniotic fluid and exosome products 'have [not] 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 FDA-approved stem cell products in the United States are blood-forming (hematopoietic progenitor) cells from umbilical cord blood, approved only for disorders of blood production, and there are currently NO FDA-approved exosome products.

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

9. In a nationally representative Finnish population sample of 602 adults aged 41-76 who had bilateral 3-Tesla shoulder MRI regardless of symptoms, rotator cuff abnormalities were found in 98.7% of participants (25% tendinopathy, 62% partial-thickness tear, 11% full-thickness tear). Abnormalities were present in 96% of ASYMPTOMATIC shoulders. Only full-thickness tears were more common in symptomatic shoulders, and that difference all but disappeared after adjustment (absolute difference 0.8%, 95% CI -3.4% to 6.0%).

   Ibounig T, et al. — Incidental Rotator Cuff Abnormalities on Magnetic Resonance Imaging.. JAMA Intern Med, 2026. DOI: 10.1001/jamainternmed.2025.7903.