Obesity is a global epidemic of 2.1 billion people and a well known cause of osteoarthritis. Joint replacement in the obese attracts more complications, poorer outcomes and higher revision rates. It is a reversible condition and the fundamental principles of dealing with reversible medical conditions prior to elective total joint replacement should apply to obesity. The dilemma for orthopaedic surgeons is when to offer surgery in the face of a reversible condition, which if treated may obviate joint replacement and reduce the risk and severity of obesity related disease in both the medical arena and the field of orthopaedics.

Not all questions can be answered by prospective randomised controlled trials. Registries were introduced as a way of collecting information on joint replacements at a population level. They have helped to identify failing implants and the data have also been used to monitor the performance of individual surgeons. This review aims to look at some of the less well known registries that are currently being used worldwide, including those kept on knee ligaments, ankle arthroplasty, fractures and trauma.

Chris Lavy is an orthopaedic surgeon in Oxford (UK) who lived and worked in Malawi for ten years. There he helped build an orthopaedic hospital and research unit. He was also one of the founders of COSECSA, the regional college of surgeons for East and Central Africa in 1999.