Remember that TCM Illnesses are very much like blanket conditions. So, Xue Bi (Blood Impediment) is anytime that blood is impeding something. It is often used to replace the wording for Bony Bi in regards to arthritis (I believe on page 168 that is a fill-in-the-blank portion w the chronic diseases. Please add: Bony Bi/Xue Bi. DVT/Raynauds are the same! You are correct that it is anytime blood is obstructing. For the arthritis kind, the blood obstructs because of an underlying zang or fu condition – so both are present. Basically, a zang fu pattern is the REASON for the Xue bi (usually – it can be from outside in as well. I.e. meridian to zang or fu).
Does that help?