One of my Buff Orpington's has a bad limp and it seems to be getting worse. The lump is on the outside of the ankle. There is no sign of scrapes and no scab on bottom of foot. I thought maybe she got caught when then automatic chicken door closed but there are no marks on her. I do not think it is related but she hasn't been right since I sprayed a White Faced Hornet nest at the peak of my house a year and a half ago. The next morning I found that some of the poisoned hornets had flown 40 feet into the chicken run. Two chickens were ill for awhile and one fully recovered and resumed egg laying. The other one stop laying and it's comb is pale and flopped over. That is the one with the lump on the ankle.