Introduction: The purpose of this study was to compare two methods for the quantification of bone marrow edema (BME) of the knee.

Materials and Methods: Forty-one patients with Bone Marrow Edema (BME) of the knee due to osteonecrosis, osteoarthritis, bone bruise or stress were included in the study. Coronal STIR images of the affected knees were obtained using either a 1.0 Tesla or a 1.5 Tesla Magnetic Resonance (MR) scanner. To monitor the BME’s progression, every knee was examined twice at a 3-month interval. Size and signal intensity of BME were semi-quantitatively assessed in consensus by two radiologists and two orthopaedic surgeons. Independently, size and signal intensity were calculated using a new computer assisted method based on grey value analysis and calculation of a threshold value between normal and edematous bone marrow. The results of the semi-quantitative method were correlated with those of the computer assisted method.

Results: The correlation coefficient was 0.89 (ìstrongî) for BME size and 0.72 (ìmedium to strongî) for BME signal intensity. For the progression of size and signal intensity, correlation coefficients of 0.78 (ìstrongî) and 0.67 (ìmediumî) were found.

Conclusion: Good correlation between semi-quantitative and quantitative methods of assessment of both size and intensity of BME was found. While the computer assisted method is time-consuming and reserved for scientific purposes, the semi-quantitative method is simple and offers to the experienced examiner a fast and simple means for BME recording in clinical practice.