The very first thing you need to do, and you need to do it now, is to take baby to an Avian vet in your area so they can check this leg out and see what is wrong. This could be a broken leg, and the swelling in knee says there may be something to do for him. The swelling may be causing the rest of the leg and foot to appear deformed as bird has no feeling in the lower part of the leg and foot. PLEASE TAKE HIM IN SO THE AVIAN VET CAN DO A QUICK XRAY OF HIS LEG TO SEE IF THEY CAN FIX THIS. Otherwise, your baby bird WILL NOT EVER BE ABLE TO SIT A PERCH and euthanization may be necessary. The vet may be able to fix his leg, and that would give him a chance at life. At least, give him a CHANCE at a normal life by taking him on in. As for just now seeing this, baby birds should be taken out and weighed every day to make sure they gain weight everyday. If one does not gain weight, then all need to go to Avian vet and be treated for possible bacterial infection which is very common with baby birds.
Let us know what vet said about his leg, and the baby will remain in prayers for his complete recovery.
