What Is a BMAC Injection?
A BMAC joint injection uses bone marrow aspirate concentrate, a preparation made from your own bone marrow. Marrow is collected through a needle and processed before injection. BMAC contains a mixture of cells and other biological components. It is not a purified stem cell product, and a bone marrow injection has not been shown to reliably rebuild worn joint cartilage.
This guide explains what the procedure involves, what research can and cannot tell you, and questions to discuss before deciding on treatment.
Does BMAC Help Knee Arthritis?
BMAC has been studied for knee osteoarthritis, but improvements reported after an injection do not establish that it works better than other treatments. In the 2023 MILES randomized trial, none of three cell-based injections, including BMAC, was better than a corticosteroid injection for knee pain at one year. The study also found no significant improvement in its MRI osteoarthritis score. Read the trial.
Results from one joint, preparation, or study do not establish effectiveness for another condition. Pain relief and cartilage regrowth are different outcomes. Ask what evidence supports the specific treatment proposed for your diagnosis and how its likely benefits compare with rehabilitation, medication, other injections, or a surgical opinion when appropriate.
Is BMAC a Stem Cell Treatment?
Bone marrow contains a small proportion of cells with the potential to develop into other tissues. Concentrating marrow does not create a standardized dose of those cells. Preparation methods and the resulting mixture vary. The presence of cells or growth factors does not by itself prove that an injection will repair a joint. AAOS describes the clinical evidence for orthopedic stem cell treatments as limited. See the AAOS patient guide.
What BMAC Treatment Involves
Bone marrow is commonly collected from the iliac crest, the upper rim of the pelvis. The area is numbed, marrow is drawn through a needle, and the sample is processed before injection. Unlike platelet-rich plasma, or PRP, which starts with a blood sample, BMAC requires a bone marrow collection procedure. Details depend on the preparation and treatment plan. Read a review of BMAC preparation.
Before agreeing to treatment, ask who will perform each step, what pain control is planned, whether imaging will guide the injection, and whether you need a ride home. Tell your clinician about medicines, allergies, infections, and bleeding problems. Do not stop prescribed medicines without individual instructions.
Recovery and Risks
Marrow collection and injection can cause pain, bruising, bleeding, or infection. Using your own tissue does not eliminate risk. Ask for written instructions about wound care, activity, pain medicines, rehabilitation, and follow-up. There is no single recovery schedule that fits every diagnosis and procedure.
Contact the treating team promptly for fever, drainage, spreading redness, or increasing pain and swelling after the procedure. Seek emergency care for trouble breathing, chest pain, or sudden severe weakness. Do not wait for a routine follow-up appointment if symptoms suggest a serious complication.
Agree on a reassessment plan before treatment: which activities or symptoms will be measured, when progress will be reviewed, and what the next step will be if you do not improve.
FDA Status and Florida Requirements
The FDA has not approved regenerative medicine therapies for orthopedic conditions such as osteoarthritis. A device used to prepare an injection and the injection's intended medical use are separate regulatory questions. Claims about a device's clearance do not establish that a BMAC joint treatment is FDA-approved. Read the FDA patient information.
Florida has specific laws concerning stem cell therapy, with definitions, conditions, and exclusions. Their application depends on the actual preparation and use. Ask the treating physician to explain the applicable requirements and informed consent for your proposed treatment. These laws should not be read as a blanket approval of every BMAC procedure. See Florida Statutes 458.3245 and 459.0127.
Questions to Ask Before a BMAC Joint Injection
- What is causing my symptoms, and what other treatments should I consider first?
- What evidence supports this preparation for my particular condition?
- What benefits are realistic, and what remains uncertain?
- What are the collection and injection risks in my situation?
- What is the full cost, including follow-up, and what has my insurer confirmed in writing?
- How will we judge whether treatment helped, and what happens if it does not?
Start with an assessment of your condition and a discussion of the available options. You can review our treatment guides or use the consultation link to discuss your questions. This page does not establish that BMAC is appropriate for you or replace individual informed consent.