If you’ve had an MRI for knee pain, your report may mention ‘bone marrow edema,’ ‘subchondral signal change,’ or ‘bone marrow lesions.’ These terms often appear almost as afterthoughts — mentioned briefly, rarely explained, and almost never specifically treated. Yet research has established that bone marrow lesions (BMLs) are the single strongest MRI predictor of pain intensity in knee osteoarthritis. They are also one of the most important predictors of how quickly your knee will get worse over time.
The fact that BMLs are so frequently overlooked in clinical practice is one of the most significant gaps between what the research shows and what patients actually receive. If you’ve already read my posts on bone-on-bone knee arthritis and intraosseous stem cell injection, this post goes deeper on the specific MRI finding that most strongly predicts both pain and outcome.
What Are Bone Marrow Lesions?
Bone marrow lesions represent areas of microdamage, trabecular bone stress, edema, and cellular changes within the subchondral bone — the dense bone layer just beneath the articular cartilage. They show up on MRI as areas of abnormal bright signal on fluid-sensitive sequences.
They are not simply ‘bone bruises’ from trauma. In the context of knee osteoarthritis, BMLs reflect chronic mechanical overload and the biological breakdown that occurs at the osteochondral interface — the zone where bone meets cartilage. They are a sign that the structural stress on the knee is exceeding what the tissue can manage, and they are actively contributing to both pain and disease progression.
Why Bone Marrow Lesions Matter — The Research
- BMLs are the strongest MRI predictor of pain in knee osteoarthritis — stronger than cartilage loss, osteophytes, or synovitis
- Larger BMLs predict faster cartilage loss over time
- Persistent BMLs after treatment are a strong independent risk factor for eventual total knee replacement
- In Hernigou et al.’s 15-year randomized trial, persistent BMLs larger than 3 cm³ after cell therapy carried a hazard ratio of 4.42 for subsequent TKA — regardless of OA grade (PMID: 32322943)
That last finding is particularly important. Even when OA grade is controlled for, the behavior of bone marrow lesions after treatment is one of the strongest predictors of whether a knee will need replacement. BMLs are not incidental findings. They are a central part of the disease.
BML Size, Location, and What the Numbers Mean
Not all bone marrow lesions carry the same clinical weight. Size and location matter significantly for both prognosis and treatment planning:
Size: The Hernigou data showed that BMLs larger than 3 cm³ that persist after treatment carry a hazard ratio of 4.42 for subsequent total knee replacement — making lesion size one of the most powerful prognostic factors in knee OA, independent of radiographic grade. Smaller lesions respond better and are more likely to regress with targeted treatment.
Location: BMLs in weight-bearing zones — particularly the medial tibial plateau and medial femoral condyle in patients with varus alignment — are the most clinically significant. These lesions are under the highest mechanical load and the least likely to resolve without targeted intervention.
Correlation with pain: A prospective longitudinal analysis from the Osteoarthritis Initiative by Driban et al. confirmed that BML volume is significantly associated with both current pain intensity and site-specific cartilage loss over 2.7 years. Larger lesions predicted worse pain and faster structural deterioration — making them a critical target for any meaningful treatment strategy. (PMID: 24020939)
The practical implication: if your MRI report mentions bone marrow lesions, the size and location of those lesions should be specifically reviewed before any treatment plan is recommended. This is part of every MRI review I do at consultation.
Why Standard Treatments Don’t Address Bone Marrow Lesions
Cortisone injections suppress inflammation in the joint space. Cortisone does not penetrate subchondral bone in clinically meaningful concentrations. It does not reach the BML.
Hyaluronic acid lubricates the joint. It does not reach the subchondral bone.
Standard intraarticular PRP and BMAC injections deliver growth factors and cells into the joint space — which modifies the intraarticular environment but does not directly address the bone marrow pathology.
This is why patients with significant BMLs often have incomplete responses to these treatments, and why a different approach — one that directly targets the bone — may produce better results.
How BMAC Targets Bone Marrow Lesions — and Why Delivery Matters
Because BMAC is derived from bone marrow itself, it is biologically native to the environment where BMLs occur. When delivered intraosseously — directly into the subchondral bone lesion through the cortical bone under fluoroscopic guidance — BMAC provides:
- Mesenchymal stem cells that can differentiate into osteoblasts and support subchondral bone repair
- Anti-inflammatory cytokines that address the chronic bone marrow inflammation driving the lesion
- Growth factors including BMP-2 and TGF-β that support bone matrix remodeling
The Hernigou research demonstrated that this approach produces BML regression over 24 months and meaningfully reduces the long-term risk of knee replacement. This is the only treatment with evidence for actually addressing the BML rather than simply managing symptoms around it.
Critically — intraarticular injection alone does not reach the bone. Standard joint injections deliver medication into the joint space, separated from the subchondral bone by the calcified cartilage layer and cortical bone above it. This is why patients with significant BMLs often have incomplete responses to cortisone, hyaluronic acid, and even standard intraarticular PRP or BMAC. The treatment is being delivered to the wrong address.
Intraosseous BMAC — advancing a specialized needle through the cortical bone into the confirmed lesion under fluoroscopic guidance — delivers stem cells directly to the pathological tissue. This is a technically demanding procedure requiring specific training in intraosseous access technique that most practices, including most clinics offering standard BMAC joint injections, do not offer.
At our clinic, I almost always combine intraosseous BMAC with bone marrow-derived PRP — produced from the same bone marrow aspirate rather than a separate blood draw — delivered intraticularly simultaneously. One aspiration yields both the cellular concentrate for the bone and the growth factor-rich plasma for the joint. The full biological yield of the procedure addresses both layers of pathology in a single session.
For more detail on the intraosseous technique and the Hernigou research supporting it, see: Intraosseous Stem Cell Injection for Knee Arthritis: What the Hernigou Research Actually Shows.
How Do I Know If I Have Bone Marrow Lesions?
BMLs are only visible on MRI — they do not show up on X-ray. If you’ve had an MRI of your knee, look at the report for phrases like:
- ‘Bone marrow edema’
- ‘Subchondral signal change’
- ‘Bone marrow lesion’
- ‘Subchondral edema pattern’
If any of these are mentioned and have not been specifically addressed in your treatment plan, bring your MRI to a consultation so we can review it directly. The size, location, and extent of BMLs all affect how we approach treatment. Learn more about bone marrow lesion treatment options.
Frequently Asked Questions
Can bone marrow lesions heal on their own?
Some BMLs from acute trauma resolve with rest. BMLs associated with chronic OA tend to persist and worsen over time without targeted treatment — and their persistence predicts faster disease progression.
My doctor didn’t mention my bone marrow lesions — should I be concerned?
It depends on the clinical context, but it’s worth raising. BMLs are frequently noted in MRI reports without being discussed specifically in the treatment plan — partly because most conventional treatments don’t directly address them. If you have significant BMLs and are still experiencing significant pain, targeted treatment may be an option worth discussing.
Are bone marrow lesions always in the knee?
No. BMLs can occur in any joint — hip, shoulder, ankle, spine (where they are called Modic changes). They are most extensively studied in the knee, but the same principles of subchondral bone pathology apply to other joints.
Can BMAC be combined with PRP for bone marrow lesions?
Yes — and this is almost always how I approach it. When bone marrow is aspirated for BMAC, the same sample yields both the cellular concentrate and a bone marrow-derived PRP fraction. I use the BMAC intraosseously into the confirmed lesion under fluoroscopic guidance, and the bone marrow-derived PRP intraarticularly to address the joint space environment simultaneously. This integrated approach uses the full biological yield of a single aspiration to address both the bone-level and joint-level pathology in one procedure.
How do I know if intraosseous injection is appropriate for my specific lesions?
Candidacy for intraosseous injection depends on the size, location, and MRI characteristics of your specific bone marrow lesions. At consultation I review your MRI directly — looking at lesion volume, location within the tibial plateau or femoral condyle, and the relationship to areas of cartilage loss. Lesions that are large, located in weight-bearing zones, and correlated anatomically with your pain symptoms are the strongest candidates for targeted intraosseous treatment.
If you’re dealing with knee pain and bone marrow lesions and want to understand your treatment options and want to explore whether regenerative medicine is right for you, schedule a consultation at our Miami clinic. You can also book online through ZocDoc. We’ll review your imaging, your history, and your goals and put together a plan that makes sense for your specific situation.
Learn more: BMAC stem cell therapy | PRP therapy | Regenerative medicine in Miami | Regenexx provider Miami | About
References
- 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.
- Driban JB, et al. Evaluation of bone marrow lesion volume as a knee osteoarthritis biomarker: longitudinal relationships with pain and structural changes. Arthritis Res Ther. 2013;15(5):R112. PMID: 24020939.
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.