Acute non-traumatic marrow edema syndrome in the knee: MRI findings at presentation, correlation with spinal DEXA and outcome.

PURPOSE: The aim of the study was to present the MRI findings of non-traumatic edema-like lesions presented acutely in the adult knee and to correlate them with the 3-year outcome and the bone mineral density (BMD) in the spine.

MATERIALS AND

METHODS

Ninety-eight patients (40 men, 58 women, mean age 60.1+/-11 years, age range 27-82 years), were followed up clinically as well as with MR imaging, when indicated, for at least 3 years. Patients were classified according to presentation in 3 groups (A: bone marrow edema (BME), B: BME and subchondral fracture, C: BME and articular collapse) and according to outcome in 2 groups (A: reversible BME, B: articular collapse). BMD measurements of the spine were carried out in males over 70 and females over 60 years old using DEXA.

RESULTS

The isolated BME pattern was observed in 64.3% (Group A), subchondral fractures without articular collapse in 11.2% (Group B) and articular collapse in 24.5% (Group C). Significant differences were found among the 3 groups at presentation, regarding the age, sex, BMD, affected area and duration of symptoms prior to imaging (p<0.05). Localization of the lesions in the weight-bearing areas of the knee was shown in 100% of C, in 90.9% of B and in 50.8% of A. The duration of symptoms prior to imaging was longer in C (7.6+/-2.8m) than in A (2.5+/-1.7m) and B (4.0+/-3.2m) (p<0.05). Group B progressed to articular collapse in 45.5%, the rest demonstrating a favourable outcome. Group C showed clinical improvement in 75% and persistent symptoms that required knee arthroplasty in 25% of cases. Articular collapse was the final outcome in 29.6% and transient BME in 70.4% of patients. These two groups showed significant differences regarding the age (p approximately 0), sex (p=0.002), low BMD (p=0.004), affected area (p approximately 0), presence of subchondral sparing (p approximately 0), duration of symptoms prior to imaging (p approximately 0), time from onset of symptoms to the final outcome (p approximately 0) and need for arthroplasty (p=0.001). None of the patients with transient BME syndrome eventually progressed to articular collapse.

CONCLUSION

In the context of acute non-traumatic knee BME, the age and sex of the patient, the duration of symptoms before imaging, the pattern of BME, and the BMD appear to correlate with the final outcome.