Regenerative injections: PRP, stem cells and prolotherapy

For knee and hip osteoarthritis the evidence-based injection is intra-articular glucocorticoid; PRP and stem cells are strongly recommended against, and no injectable has been shown to rebuild cartilage.

1. Glucocorticoid is the injection the guideline backs. The 2019 ACR/Arthritis Foundation guideline strongly recommends intra-articular glucocorticoid for knee and hip OA and conditionally prefers it over other intra-articular agents because its evidence is of considerably higher quality ¹.
2. PRP is strongly recommended against. For knee and hip OA, the ACR cites heterogeneity and lack of standardized preparations, so it is often unclear exactly what is injected ¹.
3. PRP does not regrow cartilage. In RESTORE, 288 adults with medial knee OA received three weekly leukocyte-poor PRP or saline injections; at 12 months neither pain nor medial tibial cartilage volume differed ².
4. Structural meta-analysis agrees. A 2026 meta-analysis of 12 trials found limited and inconsistent PRP effects on imaging-based structure, with no consistent benefit for medial tibial cartilage or defect progression ³.
5. Other injectables also fall short. The ACR strongly recommends against stem cell injections for knee or hip OA and conditionally against prolotherapy and intra-articular botulinum toxin, citing small trials and small or absent effects ¹.
6. Bisphosphonates in CRPS: modest and short-lived. A 2026 meta-analysis of 11 placebo-controlled trials found bisphosphonates may reduce CRPS pain at more than 4 weeks to 3 months, with little or no difference at 3–6 months and probably more adverse events ⁴.

"Rebuilds cartilage" is not a supported claim for PRP or stem cells; an exam answer promising structural repair from an injection is almost always wrong ²³.

• Hyaluronic acid is conditionally recommended against for knee OA and strongly recommended against for hip OA ¹.
• When restricted to low risk-of-bias trials, the hyaluronic acid effect versus saline approaches zero ¹.
• Ultrasound guidance is strongly recommended for hip joint glucocorticoid injection ¹.
• RESTORE pain change at 12 months: −2.1 with PRP versus −1.8 with saline, a non-significant difference ².
• Of 31 RESTORE secondary outcomes, 29 showed no between-group difference ².
• Bisphosphonate CRPS trials were 97% type I and included formulations not approved in the US, such as neridronate and clodronate ⁴.
• The ACR makes no PRP, stem cell or prolotherapy recommendation for hand OA because they have not been evaluated there ¹.

• Calling PRP "conditionally recommended" for knee OA; it is strongly recommended against ¹.
• Assuming leukocyte-poor PRP preserved cartilage in RESTORE ².
• Choosing stem cells as a safer "natural" option; the ACR also strongly recommends against them ¹.
• Treating bisphosphonates as durable CRPS therapy; medium- and long-term benefit is not shown ⁴.