Sulfur Colloid Technetium Scan. A nuclear radiology technician will inject 0.25cc of technetium sulfur colloid into the first through third web spaces of the feet in both lower extremities. In healthy controls the transit time from the feet to the aortic bifurcation is about 30 minutes. The transit time of the tracer will be measured in both lower extremities at the knee, inguinal ligament and at the aortic bifurcation. Images will be obtained with a nuclear camera according to standard protocol serially over the first hour and delayed images acquired in 4 to 6 hours if necessary. Three subjects who have responded to certolizumab will have the scan repeated at 18 weeks as outlined above.