The theme of this work is the application of the engmeermg theory of frictional torque to total hip replacement. The author adhered tenaciously to this theory, involving the use of a small-diameter femoral head, throughout the epoch when the large-diame ter, metal-to-metal design dominated the field. During that considerable period general satisfaction with the early results rendered criticisms of the large-diameter head unwelcome. There was a formidable array of counter criticism: the small head would pierce a film of synovial fluid; the small head would wear the socket too rapidly; the small head would always have a high risk of dislocation; detachment of the trochanter, to achieve precise orientation for the small head, was unacceptable. But all these objections have now been largely overcome. Lubrication of high molecular weight polyethylene (HMWP) on metal is now accepted as being mainly by the boundary regime with thick fluid films playing no part. We now know that HMWP can indeed tolerate the very high stresses imposed by the small head and in tribological theory there may even be some advantage in high stress. Dislocation is now known not to be an automatic sequel to the small head.

Early in its development, the subject matter of any field of surgery is too ill-defined and opinions are too fluid for the production of a book on the subject to be possible. Late in its development, controversy is at an end, and although it is still possible to produce a textbook, it is too late to produce a book that might stimulate discussion and crystallise ideas. This book has that objective, it being the Editor's view that the field of the surgical treatment of arthritis of the knee had reached an appropriate intermediate stage in 1978 when this text was written. Three broad issues stand out as being in need of resolution before the optimum form of surgical treatment for a given knee can be defined more convincingly than is possible at present: Firstly: What symptomatic and physical features of the knee are to be recorded pre- and post-operatively, upon the basis of which comparisons can be made between the results obtained by two different surgeons or with two different tech niques. The resolution of this issue requires general agreement not only upon what features of the knee should be recorded but, crucially, upon how these features should subsequently be presented so as to characterise a particular group of knees.