Bone marrow lesions (BMLs) are areas of abnormal signal that show up on MRI scans, typically appearing bright on certain sequences because of fluid accumulation, tiny fractures, or inflammation within the bone just beneath a joint surface. They are strongly linked to osteoarthritis-related pain and cartilage loss, but they also turn up after acute injuries, in athletes with stress reactions, and in people with metabolic bone conditions. Treatment ranges from activity modification and bracing through medications, biologic injections directly into the bone, and minimally invasive surgical procedures, with the right approach depending heavily on the underlying cause.
What Shows Up on the MRI
A bone marrow lesion is not something you can see on a standard X-ray. It is an MRI finding, appearing as an ill-defined region within the bone marrow that lights up on fluid-sensitive sequences. The term replaced an older label, “bone marrow edema,” because researchers realized that what looked like simple swelling on imaging actually corresponds to a mix of changes under the microscope: microtrabecular fractures, localized death of fat cells, fibrous tissue formation, and increased fluid in the spaces between bone trabeculae. The shift in terminology matters because it acknowledges that these lesions are more complex than mere swelling.
MRI remains the only reliable way to detect BMLs. Radiologists use specific imaging sequences, along with problem-solving techniques like chemical-shift imaging, to distinguish BMLs from other conditions that can mimic them, including tumors, infections, and blood disorders.1PubMed Central. Bone marrow lesions: A systematic diagnostic approach That diagnostic flexibility is important because the list of things that can cause abnormal marrow signal is long, and treating a stress fracture like osteoarthritis, or vice versa, leads to poor outcomes.
Why They Form
BMLs can be grouped broadly into three categories: ischemic (related to blood supply problems), mechanical (related to physical loading), and reactive (related to inflammation or other processes nearby). In the context of osteoarthritis, the dominant driver is mechanical. When cartilage thins or develops defects, the underlying bone loses its cushion and absorbs forces it was never designed to handle alone. That subchondral overload creates a stress response in the bone, producing the edema pattern seen on MRI.2PubMed. Bone Marrow Lesion as a Prognostic Factor for Osteochondral Allograft Transplantation of Cartilage Defects in the Knee Joint
Beyond osteoarthritis, BMLs appear in a variety of situations. Acute trauma, such as a ligament tear or a bone bruise from a fall, commonly produces them. They show up after cartilage repair surgery as part of the healing response. Transient BML syndromes can strike seemingly out of nowhere, particularly in the hip, causing severe pain that eventually resolves on its own over months. And in rarer cases, what looks like a BML is actually the early stage of true osteonecrosis, where bone tissue dies because its blood supply has been cut off. Each of these has its own MRI pattern and clinical presentation, which is why accurate diagnosis matters before treatment decisions are made.3PubMed Central. Aetiology and pathogenesis of bone marrow lesions and osteonecrosis of the knee
The Connection to Pain and Cartilage Loss
If you have knee osteoarthritis and your MRI shows a bone marrow lesion, there is a good chance it is contributing to your pain. BMLs have been consistently linked with both pain levels and cartilage breakdown, though the relationship is not perfectly straightforward. Some people with large BMLs on imaging report relatively little discomfort, while others with modest lesions are in significant pain. The research supports an overall correlation between BMLs and symptoms, but individual variation is real.3PubMed Central. Aetiology and pathogenesis of bone marrow lesions and osteonecrosis of the knee
What makes BMLs particularly important is their role as a predictor of what comes next. A large longitudinal study found that BMLs that grew over time were nearly three times more likely to be followed by cartilage loss in the same area compared to stable lesions. Even newly developing BMLs carried a roughly 3.5-fold increased risk. On the other hand, about half of existing BMLs either shrank or resolved entirely over the follow-up period, and those that resolved carried no elevated cartilage-loss risk.4PubMed Central. Change in MRI-detected subchondral bone marrow lesions is associated with cartilage loss: the MOST Study So BMLs are not a guaranteed one-way ticket to worsening arthritis, but growing lesions are a genuine red flag.
Do Bone Marrow Lesions Predict Joint Replacement?
For people with established knee osteoarthritis, BML severity is one of the stronger MRI predictors of whether a total knee replacement will eventually be needed. A longitudinal study found that the risk of knee replacement over four years rose with increasing BML scores, with each unit increase in BML grade raising the odds by about 57%.5PubMed. Bone marrow lesions in people with knee osteoarthritis predict progression of disease and joint replacement: a longitudinal study Separate research using quantitative MRI measurements found that tibial BML volume was the best single-region predictor, distinguishing people who would go on to joint replacement from those who would not, even when measured two years before surgery.6Osteoarthritis and Cartilage. Quantitative MRI measures of bone marrow lesion volume predict total knee replacement
This does not mean everyone with a BML ends up in the operating room. It means that BMLs have prognostic value, and tracking them over time on MRI can give your clinician a better sense of whether a joint is stable or deteriorating. For the same reason, treatments that reduce or stabilize BMLs are of growing interest as potential ways to slow osteoarthritis progression.
Bracing and Unloading
The simplest conceptual approach to treating a BML caused by mechanical overload is to reduce the load. In the knee, that often means an unloading brace, which shifts force away from the affected compartment. One randomized trial found that bracing for patellofemoral osteoarthritis significantly reduced both knee pain and BML extent compared to no brace. But the picture is mixed: another trial found no difference between an unloading brace and standard physical therapy for medial compartment osteoarthritis.7PubMed Central. Conservative treatments of bone marrow lesions
More detailed biomechanical work helps explain why bracing works for some people and not others. A study using patient-specific computer modeling showed that a valgus brace reduced peak cartilage pressure directly over BMLs by about 13%, and the time-integrated pressure by 17%, during walking. Participants who achieved a meaningful pressure reduction over their BML or cartilage defect were substantially more likely to experience a clinically important improvement in knee symptoms.8PubMed Central. Valgus bracing can relocate cartilage contact pressure away from bone marrow lesions and full-thickness cartilage defects in varus-malaligned medial knee osteoarthritis The takeaway is that bracing can help, but its benefit depends on whether it successfully redirects pressure away from the damaged area. Fit, alignment, and the specific compartment involved all matter.
Extracorporeal Shock Wave Therapy
Extracorporeal shock wave therapy (ESWT) delivers focused acoustic energy into tissue and has been used for tendon problems for years. Its application to bone marrow lesions is newer but supported by encouraging evidence. A comparative study of patients with bone marrow edema in the medial knee compartment found that the treated group had an 88% reduction in edema area on MRI at six months, compared to 41% in the control group.9PubMed Central. Extracorporeal Shock Wave Therapy Is Effective in the Treatment of Bone Marrow Edema of the Medial Compartment of the Knee: A Comparative Study
A systematic review and meta-analysis pooling results across multiple conditions, including osteonecrosis of the femoral head and knee osteoarthritis-related edema, found consistent improvements in pain and function scores at one month, three to six months, and beyond twelve months, compared to control groups.10PubMed Central. The use of extracorporeal shock wave therapy for the treatment of bone marrow oedema — a systematic review and meta-analysis ESWT has also shown effectiveness for bone marrow edema syndrome in the foot and ankle, where some patients needed two courses of treatment to achieve adequate relief.11The Journal of Foot and Ankle Surgery. Extracorporeal Shock Wave Therapy in the Treatment of Bone Marrow Edema Syndrome of the Foot The mechanism likely involves stimulation of local blood flow and tissue repair pathways within the bone, though the exact biology is still being worked out.
Medications Used for Bone Marrow Edema
Several drug classes have been tried, with varying levels of evidence. Bisphosphonates, which are traditionally used for osteoporosis, have been studied because they reduce bone turnover and may help stabilize the microenvironment around a BML. In one series, most patients treated with zoledronic acid achieved complete remission, and the majority of those who had follow-up MRIs showed either complete disappearance of edema or at least a 50% reduction.12Journal of Clinical Densitometry. Research Advances in the Treatment of Bone Marrow Edema Syndrome However, a systematic review of the broader bisphosphonate literature for bone marrow edema syndrome concluded that the evidence is still too low-quality to make a definitive recommendation one way or the other.13PubMed Central. The efficacy and safety of bisphosphonates in patients with bone marrow edema syndrome/transient osteoporosis: A systematic literature review
Iloprost, a synthetic prostacyclin analog given intravenously, has been studied primarily for bone marrow edema syndrome in the hip. A review and meta-analysis found that it reduced pain, improved function, and decreased the extent of edema on MRI in the proximal femur.14PubMed Central. The Use of Iloprost in the Treatment of Bone Marrow Edema Syndrome of the Proximal Femur: A Review and Meta-Analysis Its mechanism involves improving blood flow, which makes sense for ischemic-type lesions. Denosumab, an antibody used for osteoporosis that works by inhibiting bone resorption, has also been reported to significantly reduce pain in patients with lower-limb bone marrow edema, though the evidence so far comes from retrospective data rather than randomized trials.12Journal of Clinical Densitometry. Research Advances in the Treatment of Bone Marrow Edema Syndrome
Injecting Biologics Directly into Bone
One of the more intriguing treatment developments involves injecting platelet-rich plasma (PRP) or bone marrow aspirate concentrate directly into the subchondral bone at the site of a BML. This is different from the standard intra-articular PRP injections you may have heard about for arthritis; here, the needle goes through the bone cortex and delivers the biologic material right where the lesion lives. Ultrasound guidance can facilitate placement of a smaller-gauge needle, avoiding the need for sedation in some cases.15PubMed Central. Ultrasound-Assisted Intraosseous Injection of Platelet-Rich Plasma for a Patient With Tibial Plateau Subchondral Bone Marrow Lesion
Early results are promising. A study following patients for one year after intraosseous PRP injections for knee BMLs reported significant pain reduction, improved quality of life, and measurable changes on MRI.16PubMed. Intraosseous injections of platelet rich plasma for knee bone marrow lesions treatment: one year follow-up A comprehensive review noted that the most detailed retrospective study to date showed reductions in BML volume and improved patient-reported outcomes at 12 months following subchondral PRP injection for knee osteoarthritis.17PubMed Central. Intraosseous platelet-rich plasma for osteoarthritis: a comprehensive review This remains an emerging area, and most of the evidence comes from small case series and retrospective studies rather than large randomized trials. But the logic is sound: delivering growth factors and anti-inflammatory signals directly to the site of bone damage may promote healing in ways that intra-articular injections cannot.
Subchondroplasty and Core Decompression
When conservative and injectable treatments are not enough, two surgical procedures specifically target BMLs. Subchondroplasty involves injecting a calcium phosphate bone substitute material into the lesion under fluoroscopic guidance. The idea is to fill microtrabecular voids and provide structural support to the damaged subchondral bone. A prospective multicenter study found that patients with mild-to-moderate knee osteoarthritis who underwent the procedure saw substantial pain improvement at two years, with surgery-free survivorship above 90% at that time point and only about 8% of knees requiring reoperation.18PubMed Central. Calcium-Phosphate Subchondroplasty Provides Durable 24-Month Pain Relief and >90% Surgery-free Survivorship for Tibiofemoral Bone Marrow Lesions in Mild-To-Moderate Knee Osteoarthritis
A separate prospective evaluation reported significant improvements in pain, function, and knee scores after subchondroplasty, though the survivorship rate free from conversion to total knee replacement was lower at 76% over two years. The authors framed the procedure as a way to relieve pain and potentially delay joint replacement rather than eliminate the need for it.19PubMed Central. Prospective Evaluation of Clinical Outcomes of the Subchondroplasty Procedure for Treatment of Symptomatic Bone Marrow Lesions of the Knee The difference in survivorship numbers between these two studies likely reflects differences in patient selection, with more advanced arthritis cases having a harder time avoiding eventual joint replacement.
Core decompression takes a different approach: drilling one or more channels into the affected bone to relieve intraosseous pressure and encourage new blood vessel growth. It has been used for decades in osteonecrosis of the hip. For bone marrow edema syndrome specifically, a randomized study found that patients treated with core decompression had a significantly shorter duration of pain compared to those managed conservatively.20PubMed Central. Core decompression shortens the duration of pain in bone marrow oedema syndrome It does not necessarily change the final outcome (many transient edema syndromes resolve on their own), but it speeds up recovery, which matters a lot if you are the person who can barely walk.
Bone Marrow Lesions in Athletes
Athletes are a distinct population when it comes to BMLs. Repetitive loading from running, jumping, and cutting movements creates stress reactions in bone that show up as marrow edema on MRI. These stress-related bone injuries are common in both professional and amateur athletes, and the edema pattern on imaging is often the first objective sign before a full stress fracture develops.21PubMed Central. Reviewing Bone Marrow Edema in Athletes: A Difficult Diagnostic and Clinical Approach
Management in athletes differs from osteoarthritis-related BMLs because the goal is usually return to sport rather than long-term joint preservation. Relative rest and load modification are the mainstays. A randomized controlled trial tested functional magnetic stimulation as an adjunct for athletes with tibial bone stress injuries and found that at 16 weeks, 20% of the intervention group had complete resolution of their marrow signal abnormality on MRI compared to none in the control group.22PubMed Central. Effects of Functional Magnetic Stimulation on Pain, Function, and MRI-Derived Outcomes in Athletes with Tibial Bone Stress Injury The challenge for athletes and their medical teams is distinguishing between a stress reaction that will resolve with modified training and one that is heading toward a fracture. Serial imaging and careful symptom tracking guide those decisions.
Vitamin D Deficiency and Metabolic Risk Factors
Not all bone marrow edema arises from mechanical causes. In bone marrow edema syndrome, which tends to strike the hip or knee without a clear traumatic trigger, researchers have found that metabolic factors play a meaningful role. One study found that vitamin D insufficiency or deficiency was remarkably common in these patients, affecting 92% of those who had not been taking supplements.23PubMed Central. Identification of vitamin D and other bone metabolism parameters as risk factors for primary bone marrow oedema syndrome Impaired calcium metabolism appeared to be part of the picture, suggesting that the bone in these patients may simply be less resilient to normal loading.
This has practical implications. If you develop a BML and there is no obvious mechanical or traumatic explanation, it is worth having your vitamin D and calcium metabolism checked. Correcting a deficiency will not make the lesion vanish overnight, but it addresses a modifiable factor that may have contributed to the problem and could reduce the risk of recurrence.
Blood Markers That Track With Bone Marrow Lesions
Researchers are also working on blood and urine biomarkers that correlate with BML activity. A study from the Foundation for the National Institutes of Health Osteoarthritis Biomarkers Consortium found that rising levels of certain bone-turnover markers over 12 months were associated with increased odds of BML worsening at 24 months. Meanwhile, a marker of cartilage formation was associated with decreased odds of BML progression, suggesting that active cartilage repair may be somewhat protective.24PubMed Central. Association of biochemical markers with bone marrow lesion changes on imaging—data from the Foundation for the National Institutes of Health Osteoarthritis Biomarkers Consortium
These biomarkers are not yet used in routine clinical practice, but they hint at a future where a blood test could help identify which patients with early BMLs are most likely to progress and which are likely to stabilize. That kind of risk stratification would allow clinicians to intervene earlier in the right patients and spare others from unnecessary treatment. For now, serial MRI remains the standard way to monitor BMLs over time, with the understanding that lesions that grow deserve more aggressive attention than those that shrink or stay the same.