The problems of the patellofemoral joint remain a challenge to the orthopaedic surgeon. In spite of many articles in scientific journals, an outstanding monograph, and several excellent textbook chapters, the patella is still an enigma in many respects. The etiology of patellar pain is controversial, and there is no completely satisfying explanation for its cause or its relationship to chondromalacia. Curiously, neither the widespread use of arthroscopy nor the advent of newer diagnostic tests such as CT scanning and magnetic resonance imaging have cast much light. Without a better understanding of why patellar disorders occur it is not surprising that there is no consensus on how to fix them. Arthros­ copy has contributed little except to the patient's psyche. The currently most popular surgical treatment for recurrent dislocation of the patella was first described 50 years ago. One concrete advance, albeit a small one, is a better understanding of the role of anatomical abnormalities and patellofemoral dysplasia in patellar instabilities. It gives me great pleasure that many of the contributors are, like Dr.

Foreword by: J.N. Insall
Illustrated by: L.V. Kibiuk