Sitting foot: posture dependent changes of volume, edema and perfusion of the foot. A prospective interventional study with 27 volunteers.

Background: Sitting is known to be bad for your cardiovascular health. We furthermore hypothesized that sitting posture will reduce perfusion of the foot and increase edema, possibly predisposing to disease like osteochondritis.

Methods: We included 27 healthy volunteers and performed MRI measurements including arterial spin labelling (ASL) and intravoxel incoherent motion (IVIM) perfusion as well as short tau inversion recovery (STIR) edema measurement and 3D volumetry. After randomization, the elevation of one foot during the day was used as an intervention.

Results: Intra- and interrater variability was 1-6%. ASL perfusion measurement was hindered by artifacts. IVIM perfusion showed no significant changes during supine measurements. Volumetry could demonstrate a highly significant (p = 0.00005) volume increase, while the intervention led to a significant (p = 0.0076) volume decrease during the day. However, the water content in STIR remained unchanged and the normalized (quotient bone/muscle) edema was reduced on the control side (p = 0.006) and increased on the intervention side (p = 0.01).

Conclusions: Sitting all day leads to swelling of the healthy foot. Compensation in healthy subjects seems to prevent lasting perfusion changes or edema evolution in the bone despite an increase of muscle signal and volume increase. Thus, the etiology of osteochondritis needs further studies.