Diseased Bird: House Finch with Lame Leg

I spotted this male house finch at my feeder site on January 25, 2018. Its left leg is lame. The bird perches on its right leg only and stiffly extends or folds its left leg along its flanks or props it on a branch. In one of the photos a possible growth is visible on the leg. In some of my photos the bird also appears to be fluffed out, in contrast with other house finches that were present in the tree at the same time.