I didn't notice a problem until I downloaded the image. What could cause a hawk's leg and talons to swell on on one side and have feathers on one leg and not the other. I swear that I have not altered this image except for posting purposes.
Looks to me there is nothing wrong with the RT it has just stretched its leg and clenched his "fist". There is a condition called bumble foot which does cause swelling of the various areas of the foot but I do not think this is the case here.
Erik- I agree with Roy, nothing probably wrong here, but your capture is unusual.
What the image shows is the bird standing on its left ankle, but standing normally for most birds on its tip-toes on its right leg. The unfeathered part of the leg here is the hawk's foot which includes the toes and then the "tarsometatarsus", which looks like the lower leg but it in fact part of the foot. Above that, the feathered part visible on the left is the lower leg bones, below the knee.