Only blood pressure controls movement of fluid through the capillary wall into the tissue. Therefore, people with high blood pressure often have swelling issues.

Fluid movement through the capillary wall into the tissue is governed not only by blood pressure but also by osmotic pressure. The balance between these pressures, known as Starling's law of the capillary, determines fluid movement. High blood pressure alone does not necessarily cause swelling; it's the imbalance between hydrostatic and osmotic pressures that can lead to edema.