One of the most common questions I get from patients who have done their research is: “Should I get PRP or stem cell therapy for my knee?” It’s a fair question — and one that deserves a more detailed answer than most patients receive. Both platelet-rich plasma (PRP) and bone marrow aspirate concentrate (BMAC) are powerful regenerative tools. They’re not interchangeable, and choosing the right one starts with understanding what each treatment actually does — and what your imaging and clinical picture show.
If you’ve already read my post on PRP vs. cortisone injections for knee pain, you know why I favor regenerative approaches over corticosteroids for knee osteoarthritis. This post takes the next step: helping you understand when PRP alone is sufficient and when BMAC’s additional stem cell component changes the clinical calculus.
What PRP and BMAC Have in Common
Both treatments are autologous — they use your own biology, eliminating the risk of immune reaction or rejection. Both are performed under image guidance at our Miami clinic as part of the Regenexx network — the world’s most advanced organization in regenerative orthopedics. Both are designed to do something cortisone and hyaluronic acid cannot: address the underlying tissue environment rather than suppress symptoms temporarily.
That’s where the similarities end.
How PRP Works for Knee Osteoarthritis
PRP is prepared from a blood draw. We concentrate the platelets and growth factors from your blood and inject them into the knee joint under ultrasound guidance. Those growth factors — PDGF, TGF-β, IGF-1, among others — work to reduce chronic inflammation, modify the synovial environment, and support cartilage cell survival.
The evidence for PRP in knee OA is substantial and growing. A 2024 meta-analysis by Bensa et al. pooling 35 randomized controlled trials found PRP superior to cortisone, hyaluronic acid, and saline at mid-term and long-term follow-up — with the difference meeting the threshold for clinical significance, not just statistical significance. (PMID: 39222336)
As a Regenexx provider, our PRP protocol achieves up to 20x platelet concentration using proprietary lab processing — significantly higher than the 3–5x concentration produced by standard bedside centrifuge kits used at most practices. This matters: platelet concentration directly influences growth factor delivery, and not all PRP is clinically equivalent.
How BMAC Works — and What It Adds
BMAC requires a bone marrow aspiration from the back of the pelvis rather than a blood draw. The resulting concentrate contains everything in PRP — platelets and growth factors — plus one critical component PRP does not have: mesenchymal stem cells (MSCs).
MSCs are progenitor cells that can differentiate into cartilage, bone, and connective tissue cells. More importantly for knee OA, they have potent immunomodulatory properties — meaning they can actively modify the inflammatory environment of the arthritic joint at a cellular level that growth factors alone cannot achieve.
A 2025 narrative review by Park et al. in Medicina synthesized the current clinical evidence for BMAC in knee OA, finding consistent improvements in pain and function across studies, with evidence supporting BMAC’s capacity to promote cartilage matrix maintenance, modulate synovial inflammation, and address subchondral bone pathology. (PMC12113016)
A direct comparison study by Dulic et al. enrolled patients with Kellgren-Lawrence grade II-IV knee OA randomized to BMAC, PRP, or hyaluronic acid injection. Both BMAC and PRP outperformed hyaluronic acid, with BMAC showing superior outcomes in patients with more advanced disease. (PMC8623697)
The Most Important Factor: Bone Marrow Lesions
The single most important imaging finding that shifts my recommendation from PRP to BMAC is the presence of bone marrow lesions (BMLs) in the subchondral bone.
Bone marrow lesions — visible on MRI as areas of abnormal signal in the tibial plateau or femoral condyle — are the strongest MRI predictor of pain intensity in knee osteoarthritis. They also predict the rate of cartilage loss over time. Standard intraarticular injection, whether PRP or cortisone, does not reach the subchondral bone. BMAC, when delivered intraosseously — directly into the bone marrow lesion under fluoroscopic guidance — does.
Dr. Philippe Hernigou’s landmark 15-year randomized controlled trial demonstrated that knees treated with subchondral BMAC injection had an 18% conversion rate to total knee replacement at 15 years — equivalent to the revision rate of the contralateral knee replacement in the same patients. Knees treated with intraarticular BMAC alone had a 70% conversion rate. The delivery site matters profoundly. (PMID: 32322943)
If your MRI shows bone marrow lesions, BMAC — delivered both intraosseously and intraticularly — is almost certainly the more appropriate treatment.
PRP vs. BMAC — A Decision Framework
| Factor | Favor PRP | Favor BMAC |
|---|---|---|
| OA severity | Mild to moderate (KL grade I–III) | Moderate to advanced (KL grade III–IV) |
| Bone marrow lesions on MRI | Absent or minimal | Present and significant |
| Prior regenerative treatment | First-time treatment | PRP provided partial improvement |
| Joint space | Some preserved | Near bone-on-bone |
| Cartilage loss | Early to moderate | Significant |
| Cost consideration | Lower upfront investment | Higher upfront, potentially more durable |
| Procedure complexity | Blood draw only | Bone marrow aspiration required |
This table reflects general guidance, not a rigid protocol. The right answer for each patient is individualized based on the full clinical picture.
When I Use Both Together — And Why It’s Almost Always the Case
In practice, combining PRP and BMAC is not the exception — it is almost always the approach I use. Here’s why, and why it’s clinically meaningful.
When bone marrow is aspirated from the posterior iliac crest, the sample contains both a cellular fraction and a plasma fraction. Using the Regenexx processing protocol, I process the aspirate to produce two distinct products from the same sample: the BMAC concentrate — rich in mesenchymal stem cells, cytokines, and growth factors — and a bone marrow-derived PRP, extracted from the plasma fraction of that same bone marrow aspirate.
This is an important distinction. The PRP I use alongside BMAC is not produced from a separate peripheral blood draw. It is derived directly from the bone marrow itself — which means it contains a different and arguably richer growth factor and cytokine profile than standard blood-draw PRP. Bone marrow plasma has a distinct biological composition compared to peripheral blood plasma, reflecting the unique cellular environment of the marrow.
The result is a procedure that delivers three biological components simultaneously from a single aspiration:
- BMAC — the stem cell-rich concentrate, typically delivered intraticularly and where indicated intraosseously into bone marrow lesions under fluoroscopic guidance
- Bone marrow-derived PRP — delivered intraticularly to address the joint space environment, synovial inflammation, and surrounding soft tissue
- The combined effect — mesenchymal stem cells, growth factors, and bone marrow plasma working together to address the joint at multiple biological levels in a single treatment session
This integrated approach is procedurally more sophisticated than either treatment alone — and it is something that practices using standard bedside centrifuge kits or off-the-shelf stem cell products simply cannot replicate. Producing both BMAC and bone marrow-derived PRP from the same aspirate requires the specific processing capability that Regenexx protocols provide.
For patients, this means that a BMAC procedure at our clinic is not just a stem cell injection. It is a comprehensive biological treatment using the full yield of the bone marrow aspiration — without an additional blood draw, without a separate procedure, and without leaving any of the biological value of the aspirate on the table.
The Regenexx Difference — Why Provider Quality Matters
Not all PRP and BMAC is equivalent. Many clinics in Miami advertising “stem cell therapy” use amniotic or umbilical cord products that independent research has shown to contain no viable living stem cells. BMAC uses your own living bone marrow cells — harvested and concentrated the same day, with viable MSCs confirmed by lab processing.
As a Regenexx network provider, I use proprietary protocols developed and refined over more than 15 years of clinical practice, backed by the largest outcomes registry in regenerative orthopedics. You can review published Regenexx knee outcomes data at regenexx.com/outcomes.
I also bring fellowship training in spine, sports, and musculoskeletal medicine from the University of Pennsylvania and dual board certification in Physical Medicine & Rehabilitation and Pain Medicine to every procedure. Learn more about my background and clinical approach on the About page.
What About Cost?
PRP is typically less expensive than BMAC because the procedure is simpler — a blood draw versus a bone marrow aspiration with in-office processing. Neither is currently covered by standard health insurance. For patients with mild to moderate OA without significant BML involvement, starting with PRP and reassessing at 3–6 months is often the most cost-effective approach. For patients with more advanced disease, the investment in BMAC upfront may be more appropriate than repeating PRP multiple times with incomplete results.
Frequently Asked Questions
Can I switch from PRP to BMAC if PRP doesn’t work well enough?
Yes — and many patients do exactly this. PRP is a reasonable first step for mild to moderate OA. If the response is meaningful but partial, BMAC is the logical next treatment. The two are complementary, not competing.
Is BMAC always better than PRP for knee pain?
Not always. For early OA without bone marrow lesion involvement, PRP often produces excellent results and there’s no clinical reason to add the complexity of bone marrow aspiration. BMAC is the better option when disease severity and imaging findings warrant it — not as a default for every patient. It is also worth noting that in practice, I almost always deliver bone marrow-derived PRP alongside BMAC — produced directly from the same bone marrow aspirate — so the question is less often ‘PRP or BMAC’ and more often ‘PRP alone vs. BMAC plus bone marrow-derived PRP together.
Does image guidance matter for knee injections?
Yes — significantly. All PRP and BMAC injections at our clinic are performed under ultrasound guidance for accurate intraarticular placement. For intraosseous BMAC into bone marrow lesions, fluoroscopic guidance is used. Injections performed without image guidance have a meaningful miss rate. I do not perform blind injections.
What does the ‘Regenexx’ affiliation mean for my treatment?
It means the protocol, processing standards, and outcome tracking I use are held to the highest standards in regenerative orthopedics — stricter credentialing, higher concentration processing, and outcomes tracked in the largest registry in the field. Learn more on the Regenexx Miami page.
How many injections will I need?
For PRP, most patients receive 2–3 injections in an initial series, spaced 4–6 weeks apart. BMAC is typically performed as a single procedure with re-evaluation at 3–6 months. The need for additional treatment depends on your response and disease severity.
Can BMAC or PRP help with bone-on-bone knee arthritis?
Many patients with significant joint space narrowing — including near bone-on-bone changes — have experienced meaningful improvement with BMAC, particularly when combined with intraosseous injection into bone marrow lesions. Results depend on the extent of degeneration and patient factors. Learn more on the BMAC for knee pain page.
If you’re dealing with knee osteoarthritis and trying to decide between PRP and BMAC, the best starting point is a consultation where we can review your imaging and clinical picture together. Schedule a consultation at our Miami clinic, or book online through ZocDoc.
Learn more: PRP for knee osteoarthritis | BMAC stem cell therapy | Regenerative medicine Miami | Regenexx provider Miami
References
- Bensa A, et al. Comparative effectiveness of intra-articular injections for knee osteoarthritis: a systematic review and meta-analysis of 35 randomized controlled trials. EFORT Open Rev. 2024. PMID: 39222336.
- Hernigou P, Delambre J, Quiennec S, Poignard A. Human bone marrow mesenchymal stem cell injection in subchondral lesions of knee osteoarthritis: a prospective randomized study versus contralateral arthroplasty at a mean fifteen year follow-up. Int Orthop. 2021;45(2):365-373. PMID: 32322943.
- Park D, et al. Bone Marrow Aspirate Concentrate (BMAC) for Knee Osteoarthritis: A Narrative Review of Clinical Efficacy and Future Directions. Medicina. 2025. PMC12113016.
- Dulic O, et al. Bone Marrow Aspirate Concentrate versus Platelet Rich Plasma or Hyaluronic Acid for the Treatment of Knee Osteoarthritis. Medicina. 2021. PMC8623697.
Disclaimer: This post is for educational purposes only and does not constitute medical advice. Results from regenerative treatments vary by individual and not all patients are candidates. Please schedule a consultation to discuss your specific condition and treatment options.