Bone marrow lesions are changes observed within the spongy tissue inside bones, often identified through advanced imaging. These alterations in bone marrow signal intensity are linked to various underlying conditions affecting bone health. Their presence indicates a localized response within the bone structure, prompting further investigation to understand their origin and implications.
What Are Bone Marrow Lesions?
Bone marrow lesions (BMLs) are areas within the bone marrow that show altered signal intensity, most commonly detected using Magnetic Resonance Imaging (MRI). Initially, they were often called bone marrow edema, believed to represent fluid accumulation. However, research clarified that BMLs encompass a broader range of changes, including normal tissue, fibrosis, necrosis, bleeding, and microfractures.
Common types of BMLs include bone marrow edema, which often indicates inflammation or injury. Other forms are contusions, or bone bruises from trauma, and stress reactions from repetitive stress. These lesions can develop in any bone.
Causes and Symptoms
Bone marrow lesions can arise from various factors, including direct physical trauma and degenerative processes. Traumatic injuries like fractures or bone bruises are common, especially in athletes or those in high-impact activities. Stress fractures, small cracks from overuse, can also cause bone marrow abnormalities.
Degenerative conditions, such as osteoarthritis, frequently contribute to BMLs. In osteoarthritis, BMLs are linked to structural damage in the subchondral bone, increased pain, and disease progression. Inflammatory processes, like bone or joint infections (e.g., osteomyelitis, septic arthritis), can also cause significant bone marrow abnormalities. Less common causes include metabolic conditions, avascular necrosis (bone tissue death due to lack of blood supply), and certain tumors.
Localized pain is the most common symptom of bone marrow lesions. This pain varies in intensity and may worsen with activity or weight-bearing. Patients may also experience stiffness in the affected joint, particularly after inactivity. Swelling around the joint, tenderness to the touch, and restricted movement are other frequent symptoms.
Identifying Bone Marrow Lesions
Identifying bone marrow lesions primarily relies on advanced imaging techniques, given their location within the bone. Magnetic Resonance Imaging (MRI) is considered the most effective tool for visualizing these lesions. MRI’s ability to differentiate between various soft tissues and detect subtle changes in bone marrow signal intensity makes it superior to other imaging modalities for this purpose. On an MRI scan, BMLs typically appear as areas of high signal intensity on T2-weighted images, often with fat suppression, indicating the presence of fluid or other pathological changes within the bone marrow.
While MRI provides detailed visualization, the diagnostic process also incorporates other important steps. A thorough physical examination by a healthcare professional helps to pinpoint areas of pain, tenderness, and swelling, guiding the imaging focus. Gathering a comprehensive patient history, including information about recent injuries, medical conditions, and symptom progression, is also important for understanding the potential cause of the lesion. These clinical details, combined with the detailed images from an MRI, allow medical professionals to accurately identify and characterize bone marrow lesions.
Managing Bone Marrow Lesions
The management of bone marrow lesions depends on their underlying cause and severity. Many BMLs, especially those from trauma or overuse, respond well to conservative approaches.
Conservative treatments begin with rest and activity modification to reduce stress on the affected bone or joint, allowing healing and inflammation to subside. Pain relief is often managed with over-the-counter medications like NSAIDs. Physical therapy is another common component, focusing on improving joint mobility, strengthening muscles, and restoring function. A physical therapist guides exercises and stretches to aid recovery and prevent re-injury.
When conservative measures are insufficient or the cause is more complex, invasive treatments may be considered. These include injections, such as corticosteroid injections, for localized pain relief and inflammation reduction. In rare instances, for persistent, severely symptomatic lesions or those with significant structural damage, surgical intervention might be explored. Surgical options are reserved for specific conditions like certain fractures or avascular necrosis, determined case-by-case.
The outlook for bone marrow lesions is often favorable, with many resolving with conservative treatment over weeks to months. For example, bone contusions often resolve within two to four months. However, resolution time varies widely based on the lesion’s cause, size, and location, and the individual’s overall health. Some lesions, particularly those with chronic conditions like advanced osteoarthritis, may require longer-term management to control symptoms and slow disease progression. While the appearance of a BML on MRI may not always change immediately even with symptomatic improvement, interventions can still lead to functional and symptomatic improvements.