What do people ask about a sore shoulder?

Sources

1. MACI (autologous cultured chondrocytes on a porcine collagen membrane, Vericel; STN BL 125603) IS an FDA-LICENSED cell therapy - and its approved indication is narrow and specific: repair of symptomatic, single or multiple FULL-THICKNESS cartilage defects OF THE KNEE, with or without bone involvement, in adults. It is not approved for osteoarthritis. The existence of one licensed cartilage cell therapy for focal defects is the sharpest available way to show what a licensed 'regeneration' product actually looks like, and how far it is from an injection for a worn joint.

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

2. FDA's public list of licensed cellular and gene therapy products is the checkable answer to 'is this FDA-approved?'. A product not on that list, and not being administered under an active IND, is not an approved therapy however it is described in a brochure. For orthopedics the list is short and its cartilage entry is MACI, indicated for focal full-thickness knee defects.

   US Food and Drug Administration, Center for Biologics Evaluation and Research — Approved Cellular and Gene Therapy Products. FDA, 2026.

3. The SUMMIT randomized trial treated 144 patients (mean age 33.8, mean lesion 4.8 cm2) with at least one symptomatic focal cartilage defect (Outerbridge III/IV, >=3 cm2) of the femoral condyle or trochlea. Matrix-applied characterized autologous cultured chondrocytes (MACI) improved KOOS pain (37.0 to 82.5) and function significantly more than microfracture (pain 35.5 to 70.9) at 2 years, with histological and MRI assessment of the repair tissue. This is what a positive cartilage-repair trial looks like - in young patients with a discrete hole, not a worn joint.

   Saris D, et al. — Matrix-Applied Characterized Autologous Cultured Chondrocytes Versus Microfracture: Two-Year Follow-up of a Prospective Randomized Trial.. The American journal of sports medicine, 2014. DOI: 10.1177/0363546514528093.

4. Eighty patients with a single symptomatic chronic femoral condyle cartilage defect were randomized to autologous chondrocyte implantation or microfracture and followed 14-15 years. No significant difference in clinical scores emerged at long-term follow-up; there were 17 failures in the ACI group versus 13 in the microfracture group and more total knee replacements after ACI (6 versus 3). Fifty-seven percent of surviving ACI patients and 48% of surviving microfracture patients had radiographic early osteoarthritis (KL >=2).

   Knutsen G, et al. — A Randomized Multicenter Trial Comparing Autologous Chondrocyte Implantation with Microfracture: Long-Term Follow-up at 14 to 15 Years.. The Journal of bone and joint surgery. American volume, 2016. DOI: 10.2106/JBJS.15.01208.

5. 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.

6. 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.

7. A concise review of mesenchymal stem cells for functional cartilage tissue engineering sets out the underlying problem: articular cartilage is avascular and has very limited intrinsic repair capacity, which is precisely why engineered and cell-based approaches are being pursued - and why building tissue that matches native articular cartilage in composition and mechanical function remains an unsolved engineering problem rather than a delivered clinical product.

   Tan AR, et al. — Concise Review: Mesenchymal Stem Cells for Functional Cartilage Tissue Engineering: Taking Cues from Chondrocyte-Based Constructs.. Stem cells translational medicine, 2017. DOI: 10.1002/sctm.16-0271.

8. A 2026 meta-analysis of 21 studies (1,279 patients) found leukocyte-poor PRP augmentation at rotator cuff repair reduced structural retear risk (overall RR 0.74, 95% CI 0.55-0.99), with the benefit clearest in medium-sized tears (RR 0.68). Patient-reported outcomes did NOT improve consistently, publication-bias diagnostics indicated small-study effects (Egger p=0.017), and trim-and-fill adjustment moved the estimate to a non-significant RR 0.91 (0.69-1.19).

   Dunivan Q, et al. — Leukocyte-poor platelet-rich plasma reduces retear risk after arthroscopic rotator cuff repair: a meta-analysis with mechanistic and economic evaluation.. J Shoulder Elbow Surg, 2026. DOI: 10.1016/j.jse.2026.02.018.

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.