Mountain ultramarathon results in temporary meniscus extrusion in healthy athletes

In recent literature medial meniscus extrusion (MME) was demonstrated as an age, BMI and load dependent physiological phenomenon in healthy knees. The aim of the present study was to evaluate the influence of mountain ultramarathon running on the medial meniscus extrusion (MME) in healthy athletes.

Healthy athletes of the 2017 Gore-Tex® Transalpine run (seven stages with in total 270.5 km and 16453 m altitude) with asymptomatic knee, and no history of knee injuries or surgeries were included. All athletes underwent standard knee examination, MRI to exclude further knee pathologies and ultrasound imaging (USI) for measurement of MME before the competition. Extrusion in USI was determined in supine position (unloaded) and in standing position with full weight bearing and 20° of flexion (loaded). After the 1st, 3rd, and 7th stage ultrasound measurements were repeated directly after the competition. For evaluation of recovery, ultrasound measurement of MME was repeated 2 weeks after the race. Difference between ultrasound measurements of MME was assessed by unpaired t-test with significance set at p < 0.05.

Eighteen athletes (mean age 37.4 ± 8.3 years, 5 females, 13 males) were included in the study. The mean USI MME before the race was 1.9 mm ± 0.3 mm in supine position and 2.4 mm ± 0.4 mm under full weight bearing. During the race the mean MME increased significantly compared to baseline measurements. After 7th stage the mean MME in supine position was 2.7 mm ± 0.7 mm and 3.1 mm ± 0.6 mm under full weight bearing. After 2 weeks of recovery medial meniscus demonstrated a complete reversibility of the extrusion to normal (N.S).

Medial meniscus extrusion observed under extreme loads generated by a mountain ultramarathon is a temporary and reversible phenomenon in healthy athletes. This suggests, that the meniscus has viscoelastic capacities showing short-term adaptions to high loads, which are completely reversible over time. For clinical practice assessment of the MME by ultrasound might be favorable compared to MRI due to the ability of dynamic evaluation and the easy access. Furthermore, load should be taken in account when assessing the MME and the current cut-off value of 3 mm for meniscus pathologies should be reconsidered.

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