Joint ill, also referred to as infectious arthritis or neonatal polyarthritis, is considered a life-threatening emergency in calves, requiring rapid and aggressive treatment. It is a serious infection of the joints (common sites are the hock, stifle, fetlock, carpus, and rarely the hip and shoulder). It can be caused by a number of different organisms including E. coli, Salmonella spp, Streptococcus spp, and Arcanobacterium pyogenes. It is characterized by the development of joint swelling and pain within 24 hours of onset of infection.