LDRT vs. Stem Cell and Regenerative Injections for Arthritis

Patients who want to avoid joint replacement often hear about three other treatments: platelet-rich plasma (PRP), stem cell injections, and prolotherapy. They are all sold on the same idea, helping the joint heal itself rather than masking the pain. Low-dose radiation therapy, or LDRT, takes a different path: a small amount of radiation aimed at the joint to calm inflammation. This page compares what each one is, what the research shows, and what it costs.

What PRP Is and What the Evidence Shows

Platelet-rich plasma is made from your own blood. Blood is drawn, spun in a centrifuge to concentrate the platelets, and injected into the arthritic joint. The idea is that platelets release growth factors that may calm inflammation and support the tissue in the joint^[1]. A typical course is one to three injections, sometimes with ultrasound guidance, and mild soreness afterward is expected.

Of the three regenerative options, PRP has the largest evidence base. A 2021 meta-analysis of 18 high-quality randomized trials compared PRP with hyaluronic acid for knee osteoarthritis, with 811 PRP patients and 797 hyaluronic acid patients. WOMAC scores, a standard measure of arthritis pain and function, improved by an average of about 45 percent with PRP, compared with about 13 percent with hyaluronic acid^[2].

But the guidelines are cautious. The American College of Rheumatology's 2019 osteoarthritis guideline strongly recommended against PRP for knee and hip arthritis, citing the lack of standardized preparations: what one clinic injects is not the same as what another injects^[3]. The American Academy of Orthopaedic Surgeons' 2021 knee guideline landed in the middle: a "limited" recommendation saying PRP may reduce pain and improve function in symptomatic knee osteoarthritis^[4]. The 2019 OARSI guideline did not recommend PRP, again citing heterogeneous preparations and evidence^[5].

Some physicians are more positive. Dr. Joanne Borg-Stein, a physical medicine and rehabilitation specialist writing for Harvard Health, considers PRP reasonable for people with mild-to-moderate knee osteoarthritis whose symptoms persist despite standard treatment such as exercise, weight loss, and physical therapy. She notes that people with severe arthritis or a misaligned joint should consider knee replacement instead^[1]. Responders generally get at least six to twelve months of relief, and PRP does not replace exercise and weight management^[1].

What Stem Cell Injections Are (and Are Not)

The most common stem cell procedures for arthritis use the patient's own cells. Bone marrow is drawn, usually from the hip, or fat is taken by liposuction; the sample is processed to concentrate the cells, and the concentrate is injected into the arthritic joint. The hope is that these cells may help repair damaged joint structures or reduce inflammation^[6].

Some clinics sell something different: "stem cell" products made from donor amniotic tissue or umbilical cord blood, prepared by a third party and sold to the clinic. These are the products the FDA has warned about most forcefully. After infections tied to unapproved stem cell products sent 12 people to the hospital, the FDA warned that the products at issue were "not FDA-approved or lawfully marketed," and CDC investigators found contaminated vials linked to several clinics^[7].

The evidence is thin. Rheumatologist Dr. Stanley Cohen summarized the state of it: "There are no robust large studies to confirm benefit, but there are a number of small studies suggesting that stem cells may lead to an improvement in pain." He also pointed out that 30 to 40 percent of patients in arthritis trials improve on placebo alone for months, and that effect may be what clinics are seeing^[6]. A survey of US clinics found they claimed an average effectiveness of 82 percent, with no published data to match those claims^[6].

No stem cell therapy is FDA-approved for osteoarthritis, and the ACR's 2019 guideline strongly recommended against stem cell injections for knee and hip arthritis^[3]. As Dr. Cohen put it, "this is strictly a cash business as these are not FDA-approved therapies"^[6].

Red flags to watch for: any clinic that claims its injections regrow cartilage, promise a permanent fix, or say they eliminate the need for a joint replacement is selling beyond the evidence^[6].

Prolotherapy, Briefly

Prolotherapy is a series of injections of a concentrated sugar (dextrose) solution into and around the arthritic joint, intended to trigger a mild healing response in tissues that repair slowly. A systematic review and meta-analysis of 11 studies (837 patients) found prolotherapy safe, with no major adverse effects, and potential benefits for knee osteoarthritis pain, but most of the studies were at high risk of bias^[8]. It is the least studied of the three options, and the guideline societies do not endorse it.

Where LDRT Fits

LDRT is a course of low-dose radiation aimed at the arthritic joint. The typical regimen is six sessions of 0.5 Gy each, a total of 3 Gy, given over about three weeks. For comparison, Cleveland Clinic's Dr. Chirag Shah notes that breast cancer treatment uses 40 to 50 Gy and prostate cancer 70 to 80 Gy, while LDRT for arthritis uses 3 Gy^[9].

The newest high-quality data came from a randomized sham-controlled trial of 114 patients with mild-to-moderate knee arthritis, presented at ASTRO 2025. At four months, 70.3 percent of the 3 Gy group were responders, compared with 41.7 percent of the sham group. A lower 0.3 Gy dose did not beat sham. No treatment-related side effects were reported^[10].

LDRT has something the regenerative options mostly lack: society-level treatment guidance. The German Society for Radiation Oncology (DEGRO) published consensus recommendations for low-dose radiotherapy of painful degenerative skeletal disorders, with 0.5 to 1.0 Gy per fraction and totals of 3.0 to 6.0 Gy per series^[11]. The 2026 American Radium Society appropriate-use criteria reviewed 52 studies and reported overall response rates of 60 to 90 percent for pain reduction, mobility, and quality of life, though most of that evidence comes from observational studies^[12].

Not every study is positive. A 2025 meta-analysis of twelve studies with 1,750 patients found no significant benefit of LDRT over sham for pain or function and concluded it should remain investigational for select refractory cases^[13]. The ACR/Arthritis Foundation 2019 guideline does not include LDRT among its recommended treatments for knee osteoarthritis^[3].

Side by Side

• What it is: PRP uses your own concentrated blood; stem cell procedures use your own concentrated bone marrow or fat cells; prolotherapy uses dextrose injections; LDRT uses six short radiation sessions^[1][8][10].
• Best evidence: PRP has the largest trial base of the three, beating hyaluronic acid in randomized-trial comparisons^[2]. Stem cells have no robust large trials^[6]. Prolotherapy studies are small and mostly at high risk of bias^[8]. LDRT has one positive sham-controlled trial and a negative meta-analysis, so its evidence is split^[10][13].
• Guideline status: the ACR strongly recommends against PRP and stem cell injections for knee and hip arthritis^[3]; the AAOS gives PRP only a limited recommendation^[4]. LDRT is absent from the ACR guideline but has dedicated guidance from DEGRO and the American Radium Society^[11][12].
• Regulatory status: no stem cell therapy is FDA-approved for osteoarthritis, and the FDA has issued warnings about unapproved products^[7]. LDRT is delivered in a hospital or cancer center radiation oncology department, not a cash-pay clinic^[9].
• The procedure: needle-based injections for PRP, stem cells, and prolotherapy, versus six noninvasive radiation sessions over about three weeks with no anesthesia^[1][10].
• Safety: PRP soreness after injection is expected; stem cell harvest and injection carry infection risk^[1][6]. The LDRT sham trial reported no treatment-related toxicity^[10].
• Durability: PRP responders generally get six to twelve months of relief^[1]; LDRT responder data extend to four months in the sham trial, with longer-term results split across studies^[10][13].

The Money Question

Cost is where these options differ most. PRP costs $500 to $2,500 per injection, and most insurance plans do not cover it^[1]. Stem cell injections are more expensive: a survey of US centers found prices ranging from $1,150 to $12,000, averaging about $5,000 per knee injection, all of it cash pay^[6].

LDRT works differently. It is billed like other radiation oncology care: the consultation, the planning session, and each treatment delivery are billed as separate components^[9]. Original Medicare covers outpatient radiation therapy under Part B^[14], and most major private insurance plans cover LDRT too, though some require prior authorization. You will still owe your plan's usual deductible and copays. Our insurance guide explains how to check your own plan, and our cost guide covers what to expect if you pay out of pocket.

When Each One Makes More Sense

PRP makes more sense when your arthritis is mild to moderate, you have tried the basics (exercise, weight management, physical therapy), and you are willing to pay out of pocket for a procedure with the best-studied evidence of the three. It is not the right choice for severe, bone-on-bone arthritis or a misaligned joint^[1].

Think carefully before choosing stem cell injections. There are no large robust trials confirming they work, no FDA approval for arthritis, and the price averages about $5,000 per injection in cash^[6]. If you consider them anyway, choose a practice that is upfront about how limited the evidence is and avoid any clinic that promises regrown cartilage or a permanent fix.

Prolotherapy makes more sense when you want the simplest injection option beyond cortisone, with a low complication profile, and you accept that the studies are small and biased. It has no price advantage worth quoting here, and no guideline endorsement^[8].

LDRT is worth discussing when your arthritis is mild to moderate, you prefer a noninvasive option with no needles and no anesthesia, and you accept that the evidence is split. It has dedicated guidance from two radiation oncology societies, but the 2025 meta-analysis called it investigational, so ask your radiation oncologist to walk you through both sides^[12][13].

References:
1. PRP injection for knee osteoarthritis: Does it work? Harvard Health Publishing (Joanne Borg-Stein, MD). Harvard Health
2. Belk JW, et al. Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. American Journal of Sports Medicine. 2021;49(1):249-260. PubMed
3. Kolasinski SL, et al. 2019 American College of Rheumatology/Arthritis Foundation Guideline for the Management of Osteoarthritis of the Hand, Hip, and Knee. Arthritis and Rheumatology. 2020;72(2):220-233. PubMed
4. Management of Osteoarthritis of the Knee (Non-Arthroplasty), Third Edition. American Academy of Orthopaedic Surgeons evidence-based clinical practice guideline. 2021 (PRP: "may reduce pain and improve function," strength of recommendation: Limited). AAOS
5. Platelet-rich plasma in the management of musculoskeletal disorders: a narrative review of clinical evidence and practical considerations. Frontiers in Medicine. 2026 (summarizing OARSI 2019: PRP not recommended, heterogeneity and lack of standardization). Frontiers
6. Distinguishing 'Stem Cell Hype' From Hope in Knee Osteoarthritis. Healio Rheumatology, July 2018 (Stanley B. Cohen, MD; Muschler et al., Journal of Knee Surgery survey of 273 US centers, average ~$5,000 per knee injection). Healio
7. FDA Warns Companies on Dangerous, Unapproved Stem Cell Treatments. HealthDay, December 21, 2018 (FDA warning letters; CDC report of 12 patients hospitalized with infections from unapproved stem cell products). MedicalXpress
8. Dextrose prolotherapy in knee osteoarthritis: A systematic review and meta-analysis. (11 studies, 837 patients; safe with no major adverse effects; potential pain benefits but high risk of bias.) PMC
9. Low-Dose Radiation Therapy Reemerging for Osteoarthritis. Cleveland Clinic ConsultQD (Chirag Shah, MD). ConsultQD
10. ASTRO: Low-Dose Radiation Improves Clinical Outcomes in Mild-to-Moderate Knee Osteoarthritis. HealthDay via Drugs.com, October 2025 (reporting Kim BH, et al., ASTRO 2025). Drugs.com
11. Ott OJ, et al. DEGRO guidelines for the radiotherapy of nonmalignant disorders. Part II: Painful degenerative skeletal disorders. Strahlentherapie und Onkologie. 2015;191:1-6 (German Cooperative Group on Radiotherapy for Benign Diseases). PDF
12. Dove A, et al. American Radium Society (ARS) Appropriate Use Criteria (AUC) for Low-Dose Radiotherapy for Treatment of Osteoarthritis. American Journal of Clinical Oncology. Published online May 25, 2026, ahead of print. PubMed
13. Hammadeh BM, et al. Efficacy, safety, and pain management of low-dose radiation therapy in osteoarthritis: a comprehensive systematic review and meta-analysis. Rheumatology International. 2025;45(9):210. PubMed
14. Radiation therapy coverage. Medicare.gov. Medicare.gov