What Is BMAC? A Surgeon's Guide to Bone Marrow Aspirate Concentrate

What is BMAC (bone marrow aspirate concentrate)?

Bone marrow is a source of mesenchymal stem cells, along with growth factors and signaling proteins called cytokines that may help reduce inflammation and support repair of tissues such as cartilage and bone³. BMAC is that marrow after it has been concentrated. "Aspirate" describes how it is collected: the marrow is drawn out through a needle, usually from the iliac crest, the rim of the pelvis¹. In research papers you will also see it called BMC (bone marrow concentrate) or cBMA (concentrated bone marrow aspirate)^7,8.

Stem cells are only a small part of the mix. Mesenchymal stem cells make up roughly 0.001% to 0.01% of the nucleated cells in bone marrow^3,2, which is why the marrow is concentrated and why the way it is harvested and processed matters². The concentrate also contains progenitor cells, which laboratories can count⁹. In one study of disc injections, patients whose concentrate held more of these cells tended to improve more⁹.

A 2020 review noted that BMAC has gained recognition for cartilage conditions, including osteoarthritis, because of its potential disease-modifying and regenerative benefits³.

At our practice, BMAC is one of several orthobiologic options, alongside PRP.

Is BMAC the same as "stem cell therapy"?

BMAC is often called stem cell therapy because it contains your own mesenchymal stem cells. These cells are believed to be able to develop into several tissue types, including cartilage, bone and tendon¹⁰. Bone marrow and fat are the most abundant and accessible sources of them, and bone marrow aspirate is the source most commonly reported to stimulate healing¹⁰.

The concentrate is more than stem cells. It also carries the growth factors and cytokines found in marrow^3,2. A 2025 review described BMAC as a valuable source of mesenchymal stem cells, with potential benefits in calming the inflammatory pathway involved in knee arthritis¹¹.

BMAC and other orthobiologics are not yet FDA approved for orthopedic conditions¹².

How is BMAC done?

BMAC has three steps. At our practice all three happen in one visit at Pueblo Surgery Center, a free-standing, AAAHC-accredited outpatient facility at the same address as the office, 401 Chapala Street.

• Harvest. Marrow is drawn through a needle from the iliac crest of the pelvis¹. In one study the harvest was done with the patient lying on their back, under sedation¹. We use light anesthesia, so there is no discomfort during the harvest.
• Concentration. The marrow is processed in a centrifuge to concentrate it^2,8.
• Injection. The concentrate is injected into the joint or tissue being treated¹.

The details of harvest and processing matter. A 2022 review looked at how choices such as the harvest site, syringe size, anticoagulant, and centrifuge time and speed affect the number of mesenchymal cells in the final concentrate². Because these cells are such a small share of the marrow, the review describes harvesting and processing technique as key to getting the best results².

What does the research show for knee arthritis?

Several studies have found that people with knee arthritis improved after BMAC.

• Pain and function improved. A 2024 systematic review of 8 randomized trials with 937 patients found that pain and function scores improved after BMAC, starting about one month after the injection. The authors concluded that BMAC injections provided pain relief and functional improvement in knee arthritis, and no serious adverse events linked to BMAC were reported⁴.
• Compared with hyaluronic acid. In the same review, BMAC gave better pain scores than hyaluronic acid injections at 6 and 12 months⁴.
• Compared with exercise. In a 2018 randomized trial of 48 patients, bone marrow concentrate injected with platelet products did better than exercise therapy on knee and activity scores at 3 months. After treatment, patients' scores on most outcome measures stayed improved over their starting point through two years⁷.
• Advanced arthritis. For Kellgren-Lawrence grades III and IV, a 2024 study followed 37 knees for four years after BMAC. Average IKDC knee scores rose from 56 to 73, and WOMAC scores (where lower is better) fell from 40 to 18. Thirty-five of the 37 knees improved, walking distance improved, and none needed a knee replacement during that time¹.
• Reviews. A 2025 review reported that BMAC injections have shown effectiveness in clinical trials in improving function for people with knee arthritis¹¹.

BMAC vs PRP

Both are made from your own body. PRP (platelet-rich plasma) starts with a blood draw; the blood is spun in a centrifuge to concentrate the platelets, which carry growth factors, and the result is injected¹³. BMAC starts with a bone marrow harvest from the pelvis, as described above, and adds the marrow's mesenchymal stem cells and cytokines³. The American Academy of Orthopaedic Surgeons' patient site notes that a growing body of research shows PRP is effective for mild to moderate knee arthritis, with some studies finding results that last up to two years¹³.

The two are also used together. A review of BMAC in orthopedics found published studies that combined PRP with BMAC and others that compared them in different uses¹⁰, and the 2018 knee trial above injected bone marrow concentrate together with platelet products⁷.

In practical terms, PRP needs only a blood draw¹³, while BMAC needs a marrow harvest under light anesthesia at a surgery center. The national price figures below are also lower for PRP than for stem cell injections. Our practice offers the two together as well, described on our combined approach page.

Bone marrow concentrate for degenerative disc disease and other uses

Bone marrow concentrate has also been injected into worn lumbar discs, and several studies have found that patients improved.

• A 2020 systematic review of 7 studies with 97 patients found that after a single disc injection, average back pain scores fell from 66.0 to 20.9 on a 100 mm scale and disability scores (ODI) fell from 44.4 to 19.1, with low re-injection and complication rates⁶.
• In a 2017 study, 26 patients who were candidates for spinal fusion or disc replacement surgery received bone marrow concentrate disc injections. After three years, 20 had not gone on to surgery, and their average disability scores had improved from 56.7 to 17.5 and pain scores from 82.1 to 21.9. At one year, MRI showed that 40% of patients had improved by one grade on a standard scale of disc degeneration, and none had worsened⁹.
• A 2022 study of 32 adults found that one year after BMAC disc injections, back pain, disability and quality of life had all improved, and 59.4% of patients had a clinically meaningful improvement in back pain¹⁴.
• In a 2024 multicenter randomized trial of 40 patients with chronic disc-related low back pain, patients treated with PRP or bone marrow concentrate disc injections improved significantly in pain and function. None had adverse effects, hospitalization or surgery through 12 months¹⁵.

BMAC has also been studied in other areas. A review of 36 studies covered cartilage lesions, arthritis, fractures that failed to heal and tendon injuries⁸. Patients treated for cartilage lesions showed significant clinical improvement, with MRI findings closer to healthy (hyaline) cartilage. Bone healing and time to union improved, and when BMAC was added to tendon repair, healing rates improved and the risk of re-rupture was lower⁸. A separate review described encouraging results in bone, cartilage and tendon injuries¹⁰. For hip arthritis, a 2024 review of 5 studies with 182 patients found reduced pain, better function and better quality of life in the short and middle term, with no adverse events reported⁵.

What are the risks?

A 2025 meta-analysis of 6 randomized trials (860 patients, 334 of whom received BMAC) found that complication rates after BMAC were not significantly different from those after other knee injections, including hyaluronic acid, PRP and steroids. Knee swelling was the most common complication, in 18.3% of BMAC patients¹⁶. A review of 48 studies of stem cell based knee injections, 1,924 patients in all, found transient side effects in 12.3%, mostly swelling and pain at the injection site, and no infections or embolisms. The authors concluded that in the short term these injections pose no risk of major complications¹⁷. In the three-year disc study, there were no adverse events related to the marrow harvest or the injection⁹.

How much does BMAC cost?

We do not publish prices. For a national picture:

• Stem cell knee injections: a US study of centers marketing stem cell therapy found an average of about $5,000 per knee injection, charged to patients out of pocket¹⁸.
• PRP: at top-ranked US orthopedic hospitals, a PRP knee injection had a median price of $800, ranging from $350 to $2,815. PRP is typically not covered by insurance¹⁹.

These are national figures from published studies, not our fees. At our practice, whether you are a candidate is decided at a consultation, before any financial commitment.

Who may be a candidate for BMAC?

Not everyone is. Most knee studies have enrolled people with mild to moderate arthritis, and the four-year study above looked specifically at advanced arthritis (grades III and IV)¹. The disc studies enrolled people with chronic low back pain from a degenerated disc, and in one of them patients were already candidates for spinal fusion or disc replacement^9,14.

In our order of care, physical therapy and viscosupplementation come before orthobiologics such as BMAC or PRP. Candidacy is decided at a consultation, and no injection can promise a result.

If you live in or near Santa Barbara and want to know whether BMAC makes sense for your joint, call (805) 682-1394 to book a consultation with Dr. Scheinberg.

References

1. 1. Pabinger C, Lothaller H, Kobinia GS. Intra-articular injection of bone marrow aspirate concentrate (mesenchymal stem cells) in KL grade III and IV knee osteoarthritis: 4 year results of 37 knees. Sci Rep. 2024;14(1):2665. PubMed
2. 2. Jeyaraman M, Bingi SK, Muthu S, et al. Impact of the process variables on the yield of mesenchymal stromal cells from bone marrow aspirate concentrate. Bioengineering (Basel). 2022;9(2):57. PubMed
3. 3. Kim GB, Seo MS, Park WT, Lee GW. Bone marrow aspirate concentrate: its uses in osteoarthritis. Int J Mol Sci. 2020;21(9):3224. PubMed
4. 4. Han JH, Jung M, Chung K, et al. Bone marrow aspirate concentrate injections for the treatment of knee osteoarthritis: a systematic review of randomized controlled trials. Orthop J Sports Med. 2024;12(12):23259671241296555. PubMed
5. 5. Chandrashekar S, Jeyaraman M, Mounissamy P, et al. Safety and efficacy of bone-marrow aspirate concentrate in hip osteoarthritis: a systematic review of current clinical evidence. Indian J Orthop. 2024;58(7):835-844. PubMed
6. 6. Hirase T, Jack RA 2nd, Sochacki KR, et al. Systematic review: is intradiscal injection of bone marrow concentrate for lumbar disc degeneration effective? Cureus. 2020;12(7):e9045. PubMed
7. 7. Centeno C, Sheinkop M, Dodson E, et al. A specific protocol of autologous bone marrow concentrate and platelet products versus exercise therapy for symptomatic knee osteoarthritis: a randomized controlled trial with 2 year follow-up. J Transl Med. 2018;16(1):355. PubMed
8. 8. Gianakos AL, Sun L, Patel JN, et al. Clinical application of concentrated bone marrow aspirate in orthopaedics: a systematic review. World J Orthop. 2017;8(6):491-506. PubMed
9. 9. Pettine KA, Suzuki RK, Sand TT, Murphy MB. Autologous bone marrow concentrate intradiscal injection for the treatment of degenerative disc disease with three-year follow-up. Int Orthop. 2017;41(10):2097-2103. PubMed
10. 10. Imam MA, Mahmoud SSS, Holton J, et al. A systematic review of the concept and clinical applications of bone marrow aspirate concentrate in orthopaedics. SICOT J. 2017;3:17. PubMed
11. 11. Migliorini F, Pilone M, Ascani J, et al. Management of knee osteoarthritis using bone marrow aspirate concentrate: a systematic review. Br Med Bull. 2025;153(1):ldae016. PubMed
12. 12. U.S. Food and Drug Administration. Important patient and consumer information about regenerative medicine therapies. Content current as of April 8, 2024. fda.gov
13. 13. Alaia MJ, Kelly FB (contributors). Platelet-rich plasma (PRP). OrthoInfo, American Academy of Orthopaedic Surgeons. orthoinfo.org
14. 14. Haines CM, Bhatt FR, Orosz LD, et al. Low back pain, disability, and quality of life one year following intradiscal injection of autologous bone marrow aspirate concentrate. Stem Cells Int. 2022;2022:9617511. PubMed
15. 15. Navani A, Ambach M, Calodney A, et al. The safety and effectiveness of orthobiologic injections for discogenic chronic low back pain: a multicenter prospective, crossover, randomized controlled trial with 12 months follow-up. Pain Physician. 2024;27(1):E65-E77. PubMed
16. 16. Fucaloro S, Bragg JT, Feldman MW, et al. Complication rates of bone marrow aspirate concentrate injections versus other injectable therapies for knee osteoarthritis: a systematic review and meta-analysis. J Orthop. 2025;62:36-42. PubMed
17. 17. Riggle C, McLellan M, Bohlen H, Wang D. Complications of stem cell-based injections for knee osteoarthritis: a systematic review. HSS J. 2025;21(4):476-484. PubMed
18. 18. Piuzzi NS, Ng M, Chughtai M, et al. The stem-cell market for the treatment of knee osteoarthritis: a patient perspective. J Knee Surg. 2018;31(6):551-556. PubMed
19. 19. Tiao J, Wang K, Herrera M, et al. There is wide variation in platelet-rich plasma injection pricing: a United States nationwide study of top orthopaedic hospitals. Clin Orthop Relat Res. 2024;482(4):675-684. PubMed

Reviewed by Dr. Richard Scheinberg, MD, a board-certified orthopedic surgeon in Santa Barbara with 40 years of surgical experience.