Ipsilateral ILN drains ICG from WT/pre-arthritic knees not from arthritic knees with collapsed PLN. Non-recovery ICG-NIR imaging of PLN and ILN was performed on WT mice (n = 2) following an intraarticular ICG injection into the knee, in which their abdominal cavity was opened to expose the ILN. NIR-ICG images obtained 10 minutes after injection from one of the animals are shown highlighting the ICG drainage from the injection site (black arrows) to the PLN (A dorsal view) versus the ILN (B ventral view). Note the absence of ICG signal in the PLN (circled region), and its presence in the ILN (white arrow). Similar non-recovery ICG-NIR imaging was performed on TNF-Tg mice (n = 8) with asymmetric knee arthritis, and a ventral view image of a representative animal with collapsed (left) and expanding (right) PLN is shown (C). Black arrows indicate the ICG injection site in the knee, and white arrows point to the ILN. Note that ICG has migrated to the right ILN but not the left ILN resulting in a dramatic difference in SI (179 vs. 253).