Share 'Joint swelling'

Need some help. I have an 8 yr. old KC with swelling of joints in both front legs. This seems to have come on suddenly.Vet is testing for various things. Preliminary blood work is neg. for Lyme, cancer and a arthritis. xrays have been sent to a radiologist for further study. Any ideas or publications I can read. Could this be diet related-she is on Chicken soup for the dog lover brand of dry food…