Role of diffusion-weighted magnetic resonance imaging in evaluation of bone marrow edema of the knee

Abstract

Background Bone marrow edema (BME) has not been recognized as a significant pain generator or as a primary contributor to disease until recently. BME is characterized by a nonspecific pattern of ill-defined high signal intensity on short-tau inversion recovery and T2-weighted MRI and low signal intensity on T1-weighted images. Objective To assess the value of diffusion-weighted MRI in the diagnosis and evaluation of BME at the knee region. Patients and methods This study was conducted on 130 patients referred with clinical suspicion of knee edema with or without history of trauma. They were divided into group ‘A,’ with lesions less than 15 mm, and group ‘B,’ with lesions greater than 15 mm. Their ages ranged between 9 and 75 years, with a mean age of 42 years. There were 43 females and 87 males. Results Between groups A and B, we found that bone marrow lesions (BMLs) were approximately two times larger on apparent diffusion coefficient (ADC) maps than on fat-saturated (FS) proton density (PD)-weighted turbo spin echo images. The most important value of adding the ADC-derived maps in routine MRI examination of the knee is to show additional BMLs that only can be detected at the ADC maps but could not be detected at the FS PD. Approximately 27 more lesions in 27 patients and one patient with two more lesions were detected. These nonconcordant lesions accounted totally for 29 more BMLs. Conclusion MRI is the mainstay of diagnosis, staging, and management plan of knee traumatic and nontraumatic disorders. ADC maps are more sensitive than corresponding FS PD-weighted turbo spin echo images allowing for detection of significantly more and larger BMLs. In addition, they represent a valuable add-on in knee imaging protocols.