An articular or periarticular proliferation of bone around the proximal interphalangeal joint. The articular ringbone is due to osteoarthrosis of the joint and is a progressive degenerative disease that can lead to severe lameness. Periarticular ringbone is due to a periostal reaction of the bone in the immediate vicinity of the joint due to pulling of the joint capsule or the collateral ligaments, in these cases lameness may be less severe or absent.