[tpoacher]

It's been years since I've practiced, so take my understanding with a grain of salt, but, the idea is that the swelling will be excessive, and because the space to accommodate it is limited, this can end up constricting the blood vessels and compromise blood perfusion, despite the fact that the inflammatory response is trying to 'open' them.

Therefore by artificially causing them to open slightly less, you control the swelling, and stop it from pooling so much that it then blocks blood flow completely.

The extreme scenario of this is called compartment syndrome, where the blood flow is completely blocked, leading to necrosis of the affected area; this is an orthopedic emergency, where 'fasciectomy' needs to be performed; effectively slicing open the compartments to allow the expansion to occur without compromising blood flow.