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

PurposeThe 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 methodsNinety-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.ResultsThe 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 ± 2.8 m) than in A (2.5 ± 1.7 m) and B (4.0 ± 3.2 m) (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 ∼ 0), sex (p = 0.002), low BMD (p = 0.004), affected area (p ∼ 0), presence of subchondral sparing (p ∼ 0), duration of symptoms prior to imaging (p ∼ 0), time from onset of symptoms to the final outcome (p ∼ 0) and need for arthroplasty (p = 0.001). None of the patients with transient BME syndrome eventually progressed to articular collapse.ConclusionIn 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.