Objective Assessment of short?term and mid?term changes of knee cartilage in non?professional long?distance runners before and after marathon using T2 mapping imaging. Methods Twenty?four knee joints of 12 healthy volunteers (5 males and 7 females) who participated in the marathon were examined by 3.0 T MRI one week before the race, within 12 hours after the race and two months after the race, respectively. The age ranged from 21.0 to 37.0 years. Athletes run more than three times a week, and each time was about 30 minutes. From T2 mapping we can obtain T2 value of 6 cartilage subregions of knee joint. Paired t?test was used to compare the T2 values of cartilage before and after the marathon. The comparison between the superficial and deep T2 values of cartilage was performed by independent sample t test. Results T2 mapping imaging showed that the T2 value of the superficial articular cartilage was higher than that of deep articular cartilage in pre?competition, within 12 hours after competition and 2 months follow?up, respectively (t=11.095, 10.385 and 10.102, P<0.01). The T2 value of superficial articular cartilage decreased after the competition compared with that of pre?competition (t=2.18,P<0.05), while the T2 value of deep articular cartilage showed no significant difference compared with that of pre?competition (t=1.832, P> 0.05). Except for the MTP?DZ, the T2 value of the remaining cartilage subregions showed a trend of decrease within 12 hours after the competition. There were significant differences in the subregion of MFC?DZ (t=2.110,P<0.05). At the follow?up of 2 months, cartilage T2 values of the MTP?SZ,LTP?SZ,LTP?DZ,MFC?DZ, Patella?SZ, Patella?DZ, Trochlea?SZ, Trochlea?DZ subregions showed a trend of recovery, and there was no significant difference compared with pre?competition(t=0.857,0.573, 0.146, 0.510,-0.594,-1.135,-0.812,-0.679; P>0.05). The T2 values of the LFC?SZ and LFC?DZ were lower than those before the race, with statistical significance (t=2.378, 3.147,P<0.05). Conclusion T2 value could reflect the change process of articular cartilage tissue composition in marathon runners from T2 mapping imaging. Under stress, the changes of superficial T2 value are more significant. The T2 value of knee cartilage can gradually recover to the pre?run level 2 months after running.

Objective: Assessment of short-term and mid-term changes of knee cartilage in non-professional long-distance runners before and after marathon using T₂ mapping imaging. Methods: Twenty-four knee joints of 12 healthy volunteers (5 males and 7 females) who participated in the marathon were examined by 3.0 T MRI one week before the race, within 12 hours after the race and two months after the race, respectively. The age ranged from 21.0 to 37.0 years. Athletes run more than three times a week, and each time was about 30 minutes. From T₂ mapping we can obtain T₂ value of 6 cartilage subregions of knee joint. Paired t-test was used to compare the T₂ values of cartilage before and after the marathon. The comparison between the superficial and deep T₂ values of cartilage was performed by independent sample t test. Results: T₂ mapping imaging showed that the T₂ value of the superficial articular cartilage was higher than that of deep articular cartilage in pre-competition, within 12 hours after competition and 2 months follow-up, respectively (t=11.095, 10.385 and 10.102, P<0.01). The T₂ value of superficial articular cartilage decreased after the competition compared with that of pre-competition (t=2.18,P<0.05), while the T₂ value of deep articular cartilage showed no significant difference compared with that of pre-competition (t=1.832, P> 0.05). Except for the MTP-DZ, the T₂ value of the remaining cartilage subregions showed a trend of decrease within 12 hours after the competition. There were significant differences in the subregion of MFC-DZ (t=2.110,P<0.05). At the follow-up of 2 months, cartilage T₂ values of the MTP-SZ,LTP-SZ,LTP-DZ,MFC-DZ, Patella-SZ, Patella-DZ, Trochlea-SZ, Trochlea-DZ subregions showed a trend of recovery, and there was no significant difference compared with pre-competition (t=0.857,0.573, 0.146, 0.510, -0.594, -1.135, -0.812, -0.679; P>0.05). The T₂ values of the LFC-SZ and LFC-DZ were lower than those before the race, with statistical significance (t=2.378, 3.147,P<0.05). Conclusion T₂ value could reflect the change process of articular cartilage tissue composition in marathon runners from T₂ mapping imaging. Under stress, the changes of superficial T₂ value are more significant. The T₂ value of knee cartilage can gradually recover to the pre-run level 2 months after running.