Bruce M. Rothschild is a professor of medicine at the Northeastern Ohio Universities College of Medicine and a professor of biomedical engineering at the University of Akron; he is also a research associate at the Carnegie Museum of Natural History and the University of Kansas Museum of Natural History. He offers this overview:
"The question of what diseases affected dinosaurs is an intriguing one. Actually, dinosaurs may have been healthier than people are today. As far as we can tell from the fossil record, disease was relatively rare among most dinosaurs. For this discussion, I will consider injuries as well and divide my response into the following categories: developmental abnormalities, trauma and injury, infection, osteoarthritis, tumors and structural modifications.
"One of the most prominent kinds of such abnormalities is an overgrowth of bone, called exostosis. The shoulder blade of the Allosaurus skeleton on exhibit at the Smithsonian Institution in Washington, D.C., has such an overgrowth, which transforms the bone's appearance from a long, thin rectangle (its normal shape) to a mimic of the shape of the human scapula. Exostosis has also been noted on a Triceratops jaw, possibly the result of injury.
Trauma and injury
"Fractured dinosaur bones are actually rare. Isolated injuries have been reported in Camptosaurus, Iguanodon, Deinonychus and Syntarsus. Carnosaurs (large carnivorous dinosaurs, including Tyrannosaurus rex, Albertosaurus and Allosaurus) often show evidence of the hazards of their profession. One eighth of their injuries were to the head, and roughly one quarter each were to the vertebral column and ribs, proximal (upper) forelimbs and distal (lower) hind limbs. An Albertosaurus skeleton on exhibit at the Royal Ontario Museum shows impressive evidence of surviving a broken bone, as denoted by healing of the fracture.
"An epidemiologic study conducted by Darren Tanke of the Royal Tyrrell Museum of Paleontology in Alberta, Canada examined more than 30,000 bones from horned dinosaurs (notably Centrosaurus and Pachyrhinosaurus). Tanke found a frequency of fracture of less than one in 1,000. The distribution of those fractures was intriguing. In a report that Tanke and I published together, we related mid-rib and posterior rib fractures to territorial defense and courtship behavior. Similarly, we suggested that fractures to the neural spine (the structure coming off the back of the vertebrae) of duckbill dinosaurs were damage resulting from the injuries sustained during the mating process itself.
"Whereas acute trauma and injury can produce fractures, bone can also be altered by repeated subthreshold stresses. Each individual trauma may be insufficient to produce a fracture, but repetitive exposure to such trauma can bring it about, similar to 'march' fractures that occur among military recruits. Such injuries are called stress fractures. They could perhaps be considered partial fractures and are relatively common in some horned dinosaurs. Bumps on the foot bones of horned dinosaurs were caused by stress fractures. But why did they get such fractures? One could postulate foot stamping and pawing, as is done by bulls, or long migration efforts, similar to the strains encountered by military recruits.
"Infections were quite rare; there are only isolated known examples, which have been observed in Dilophosaurus, Troodon, Camptosaurus, Allosaurus, as well as duckbill and horned dinosaurs. The most famous instance of infection might be the skull of a duckbill dinosaur (a Lambeosaurus) which shows a dental abscess. Given the size of a duckbill dinosaur's tooth row, that must have hurt! Such infections must have been either rare events or else incompatible with survival.
"The most famous claim of disease in dinosaurs relates to osteoarthritis, previously referred to as degenerative joint disease. This claim was the precipitating factor for my entry to the fascinating field of paleopathology. Researchers routinely asserted that osteoarthritis was common in dinosaurs, and I simply wanted to illustrate a lecture. My search and x-ray studies failed to identify a single example, until I saw the famous fossils of an Iguanodon herd in Brussels. Two herd members had osteoarthritis of the ankle. To date, they are the only identified dinosaurs that show signs of osteoarthritis.