(1) Measurement of agKS and HA in a blood vessel draining or close to an injured/diseased knee joint may provide more specific information about degradative changes taking place in that joint than measurement of levels of these markers in other blood vessels; (2) some HA molecules but no measurable amounts of agKS enter the blood circulation via the lymphatic system: and (3) HA but not agKS is very rapidly cleared from the blood by the liver.