Bumblefoot is actually the layman's term for the staph infection they get from a puncture wound, scratch, or other entry way into the pad of the foot.
Not every scab means the pad is infected. Some chickens are able to heal these things on their own, others no so much. Towel up the bird and clean off the pad. Soak the foot to get all the gunk off the foot before toweling if you have to. Take a good look at the pad and compare it to the other good pad. A healthy pad should have softness to it, some pads are somewhat deflated and there shouldn't be any large areas of redness to the pad.
While looking at the scab, take a tooth pic or other semi sharp tool and poke at the center of the black scab. If it is hard, that is a good sign that possibly it will heal on it's own. If there is a soft spot at the center of the scab, it may be infected. Not all birds limp with big infection.
You have two options to heal it up. You can take the simple route first to see if it may heal without surgery....Soak the foot daily in warm salt water or epsom salts for 5 to 10 mins a day. Then apply neosporin to the pad and wrap with vet wrap. Do this daily for several weeks and many times the wound and scab will heal. Do not wrap too tightly, but tightly enough to keep the dirt out. Check the toes about 5 mins after wrapping. They should not be cold, or you have wrapped too tightly.
Or, you can peel off the scab to see what is underneath. If there is pus at the surface, you will need to squeeze, dig and work the infection out. You would also soak the foot daily, pack with neosporin and wrap the foot. Use gauze over the pad and around the webbing first for long term wrapping so the latex over time, does not irritate the soft skin.
Bumblefoot does not heal incredibly fast, but if you keep the foot bandaged with neosporin, many times it will heal on it's own. Never let the scab see dirt until it is well healed. Clean and dry is the key to healing.
