The archaeology of joint disease

Abstract

Not all diseases leave their mark on the bones. The major killers of the past, such as the infectious diseases of childhood, gastroenteritis, pneumonia and septicaemia from infected wounds, as well as cardiovascular and neurological conditions, in general leave no trace. Joint disease, however, does leave its mark on the bones, and along with trauma and dental disease the arthritides comprise most of the evidence for disease in ancient humans as revealed in their skeletal remains. Diagnosis of joint disease presents problems to the palaeopathologist in that one cannot extract a family or personal history or elicit signs and symptoms from a bony skeleton, and neither can one undertake the barrage of laboratory examinations available to the modern physician. The distribution of joint disease (as well as its appearance) is of vital importance in arriving at a diagnosis, and this underlines the necessity of careful excavation and recovery of as much of the skeleton as possible. The pattern of distribution of degenerative joint disease can give an indication as to the occupation of an individual or community, and the study of ancient skeletons contributes not only to our knowledge of the history of medicine and disease, but also contributes to the understanding and practice of modern clinical medicine. Funerary archaeology, amongst other things, entails digging up ancient human skeletal remains. A wealth of information can be obtained from a study of these ancient bones. Palaeopathology, or the study of ancient disease, is just one of a long list of studies that can be undertaken on ancient bones. What I shall be doing here is to give a brief account of joint disease, which is just one of a whole gamut of disease processes available to the palaeopathologist for study. There are some fundamental differences between the study of diseases on ancient skeletons and the study of disease in modern living populations. One of the obvious differences is that one cannot extract a family or personal history from a bony skeleton. Neither can one elicit signs nor inquire about symptoms from a bony skeleton, and neither can one undertake the barrage of blood and other laboratory examinations available to the modern physician which aid in diagnosis. Another obvious difference is that without any soft tissue remains, only those diseases which leave their mark on the bones can be detected. And as not all diseases leave their mark on the bones, then the range of disease which can be diagnosed by the palaeopathologist is restricted compared with that available to the modern physician. Most of the major killers of the past, such as the infectious diseases of childhood, gastroenteritis, pneumonia, septicaemia from infected wounds as well as cardiovascular and neurological conditions, in general leave no trace on the bone. Joint disease, however, does leave its mark on the bones, and along with dental disease and trauma, the arthritides comprise most of the evidence for disease in ancient humans as revealed in their skeletal remains. Of course, before diagnosing pathology on bones, one has to be familiar with the normal appearance and variants of the bones, and one has also to exclude any pseudopathology such as postmortem erosions caused by the tooth puncture marks of scavenging carnivores. The diagnosis of joint disease from ancient skeletons is based on the evaluation of two fundamental parameters: 1. The morphology or gross appearance of the articular lesions; 2. The distribution of the lesions in the skeleton. The most commonly occurring joint disease seen in archaeological human groups is osteoarthritis, just as it is the most common joint disease of modern populations. Osteoarthritis is as old as the hills; it has even been diagnosed in the fossilised spine of a 100 million years old Comanchean dinosaur! The archaeological diagnosis of osteoarthritis depends on the demonstration of three morphological features. Firstly, there is the demonstration of porosity on a joint surface, which occurs as a result of bone degeneration on the joint surface following destruction of the cartilage. Another feature characteristic of osteoarthritis is the formation of osteophytes on the joint surface or margins of the joint. And the third diagnostic feature of osteoarthritis is the presence of sclerosis or eburnation of the joint surface. This is seen as a hard shiny surface on the bone, which is often grooved where bone has been rubbing on bone. Apart from the morphological appearance of the lesions, the other fundamental parameter used in the diagnosis of joint disease in ancient skeletons is the distribution of the lesions. We all know, for example, that osteoarthritis, rheumatoid arthritis, gout, psoriasis and ankylosing spondylitis tend to have a specific distribution in the joints of the body. And this underlines the importance of the careful excavation and recovery of as much of the skeleton as possible, so that the distribution of the lesions in the skeleton can be mapped out, as this aids in the differential diagnosis. Unfortunately, in practice, we are rarely presented with a complete and perfect skeleton. All too often, the reality is that we are dealing with fragmented and incomplete remains. And this particularly applies to the small bones of the hands and feet, which are crucial in the diagnosis of joint diseases. All too often, these small bones do not survive the burial conditions, or they are so fragile that they are lost in the excavation procedure. Another reason for the loss of these small bones can be due to the burial customs of the ancient people themselves, such as the amputation of fingers from the corpse for separate burial beneath the floor of the house. A local example of the postmortem interference with the bones of the hands and feet comes from the late Punic/early Roman tomb discovered in the middle of Tal-Barrani Road in 1993 during the course of excavation of a trench for the laying of an electricity cable. A pair of burials was discovered at the base of the trench, neither of the skeletons exhibiting any hands or feet. Examination of the contents of a ceramic jug positioned at the foot of these skeletons revealed it to contain an assortment of carpal and tarsal bones, as well as metacarpals, metatarsals and associated phalanges. For good measure it also contained three coccygeal bones as well as a wooden shroud or hairpin. But there were not enough bones to account for two full sets of hands and feet. This pair of burials must have represented the first inhumations in the tomb, and they must have been completely decomposed by the time subsequent burials took place. In fact, there were four other burials in this tomb. The mourners or relatives at the subsequent burials must have carefully collected the hand and foot bones and the coccygeal bones and placed them in the juglet. What happened to the missing bones is not known, but this is an example of postmortem interference with the skeleton resulting in partial loss of hand and foot bones, which can complicate the diagnosis of joint disease in archaeological specimens. Thus far, I have alluded to some of the problems associated with the archaeological diagnosis of joint disease. However, there is one important advantage that the archaeologist has over the modern physician. And that is that he is able to examine the joint surface directly with the naked eye without any intervening soft tissue getting in the way. He can twist and turn the bone and look into every nook and cranny of the joint surface. The benefit of this can be seen in the results of the work done by Rogers, Watt and Dieppe (1990). They examined 24 knee joints from 14 skeletons, the joints ranging from normal to those with severe osteoarthritis.