A genetic predisposition for deafness is a serious health problem for Dalmatians;  American Dalmatians exhibit a prevalence for bilateral congenital sensoneural deafness of 8%, (for which there is no possible treatment), compared with 5.3% for the UK population. Deafness was not recognized by early breeders, so the breed was thought to be unintelligent. Many breeders, when hearing testing started to become the norm, were amazed to discover that they had uni hearing dogs. Hip dysplasia is another disease that affects nearly 5% of purebred Dalmatians, causing those to experience limping, fatigue, moderate to severe pain, and trouble standing up. Most Dalmatians who eventually develop hip dysplasia are born with normal hips, but the soft tissues surrounding the joint grow abnormally due to their genetic make-up.