Femoropatellar Joint Reaction Detected During a 4486 KM Ultramarathon with Mobile MRI.

Almost nothing is known about the condition of the knee joints of multistage ultra-marathon (MSUM) runner. This is first image-based investigation of the femoropatellar joint (FPJ) using a mobile 1.5T MRI accompanying the MSUM TransEurope Foot-Race (TEFR) 64 stages over 4486 km. Twenty-two (20 male) subjects got a knee MRI-protocol at defined measurement intervals during TEFR: T2*-mapping (FLASH T2*-GRE), TIRM, and fat saturated PD -sequence. In the FPJ 12 different regions were evaluated regarding cartilage T2* and thickness changes and cartilage lesions in course of TEFR and a test on possible compounding factors (running burden, BMI, age) was done if being appropriate. No significant changes in cartilage thickness- and T2*-values were found during TEFR. In 8 runners, at least one single cartilage lesion (Grade 2-3) was found at baseline, but no significant race-related adjacent T2*-changes or progress of the defects could be detected. Analyses on compounding factors were negative. In knees with MPP (5) significantly lower adjacent T2*-values were found. The extreme running burden of a MSUM seems not to have a relevant negative influence on the FPJ tissues, even if cartilage lesions are present.

MRI Cartilage Assessment of the Subtalar and Midtarsal Joints During a Transcontinental Ultramarathon - New Insights into Human Locomotion.

MR measurements can be accurately performed during 4486 km of running, opening a window into in vivo assessment of hindfoot articular cartilage under extreme ultra-endurance loading. This observational cross-sectional study included 22 randomized participants of TransEurope FootRace between Italy and the North Cape, which was accompanied by a trailer-mounted 1.5T MRI scanner over 9 weeks. Four follow up MR examinations of subtalar and midtarsal joints were performed. Statistics of cartilage T2* and thickness were obtained. Nearly all observed joints showed an initial significant mean T2* increase of 20.9% and 26.3% for the left and right side, followed by a relative decrease of 28.5% and 16.0% during the second half, respectively. It could be demonstrated that mobile MRI field studies allow in vivo functional tissue observations under extreme loading. Elevated T2* values recovered during the second half of the ultramarathon supported the evidence that this response is a physiological adaptive mechanism of chondrocyte function via upregulation of de novo synthesis of proteoglycans and collagen. These changes occurred in a distinct asymmetric pattern leaving a "biochemical signature" of articular cartilage that allows in vivo insight into joint loading. In conclusion, the normal articular cartilage of the hindfoot is resilient and adaptive, leaving extreme endurance activities up to limitless human ambition.