MRI study of changes in knee bone marrow edema-like signal in asymptomatic amateur marathon runners before and after half-marathon running

Objective: To evaluate the incidence of knee bone marrow edema-like signal and its changes before and after running a half marathon running in asymptomatic amateur marathon runners to explore the impact of the half marathon on knee bone marrow edema-like signal. Methods: 50 asymptomatic amateur marathon runners (30 males, 20 females) were recruited. T1-weighted imaging (T1WI), fat-suppressed protein density weighted imaging (fs-PDWI) and three-dimensional double-echo steady-state (3D-DESS) sequence on the right knee were performed before and within 3 h after a half-marathon running. 20 healthy volunteers were recruited as control. According to the whole-organ magnetic resonance imaging score (WORMS) system, the involvement of bone marrow edema-like signal in 15 regions of knee was graded from 0 to 3. The results were classified and Mann Whitney U test was used for comparison between groups. Results: The total incidence of bone marrow edema-like signal in amateur marathon group was 62%. Among them, the incidence of grade 1-3 was 48% (24/50), 12% (6/50), 2% (1/50), respectively, which was statistically significant compared with the controls (P = 0.007). There was no significant difference between gender before running (P = 0.172) and after running (P = 0.162). There was no significant difference before and after running (P > 0.05). However, 3 subjects showed new lesions, 8 subjects showed progression and 4 subjects showed decreased signal. Conclusion: The occurrence of knee bone marrow edema-like signal in amateur marathon runners is more common. The lesions of bone marrow edema-like signal will show aggravation or improvement in a certain extent after the half marathon.