Open Access
Feature Article

Youth, obesity and worn knees. A trifecta of trouble

David Campbell


Associate Professor Campbell is an orthopaedic surgeon in private practice in Adelaide, SA, specialising in joint replacement.


An morbidly obese 38-year-old woman with advanced osteoarthritis has disabling knee pain. Is immediate knee replacement surgery appropriate for this patient?

Case scenario

Millie is a very overweight 38-year-old woman with a BMI of 42 kg/m2. She has advanced osteoarthritis with relentless pain, particularly in her right knee, imaging of which has shown complete breakdown of cartilage as well as bone oedema and cysts. She has three young children and is finding it difficult physically to cope with all the necessary activities of daily living. She has been told that a knee replacement cannot be contemplated until she reaches the age of 50 years.

Is this age for knee replacement a widely accepted orthopaedic guideline, or might she have been told this as part of a vigorous attempt to get her to lose weight? What can be done for Millie?


This case scenario describes an increasing problem throughout the Western World for which we are grappling to find a solution. The WHO describes obesity as a global epidemic about to surpass malnutrition and infectious disease.1 The past decade has seen an increase in obesity of 50% and evidence of its association with cardiovascular, endocrine, malignancy and musculoskeletal problems, but sadly many obese people are not aware of the dramatic reduction of both the quality and quantity of their life. 


The US Centers for Disease Control and Prevention estimates that two-thirds of obese people will have knee osteoarthritis, compared with 45% of the normal population.2 British epidemiology studies suggest a sixfold increase in knee osteoarthritis and an 18-fold increase in bilateral arthritis in people who are obese.3 People who are morbidly obese fair far worse. The patient in the case scenario, Millie, considers herself as overweight but her BMI of 42 kg/m2 classifies her as morbidly obese; if she was 165 cm tall, she would weigh 115 kg, which is considerably more than her optimal weight of 62 kg (BMI, 22 kg/m2). 

National joint registries have shown a sustained increase in the portion of total knee replacements being performed in younger patients.4,5 Over the past decade there has been a doubling in the number of men and almost tripling in the number of women in the 45 to 54-years age group having total knee replacements.5 Overall the demand for joint replacement surgery is escalating at an ever-increasing rate.


How to evaluate the patient

The standard approach of history, examination and further tests is applicable to all orthopaedic conditions. Morbidly obese patients usually have a range of comorbidities that often have far more pressing issues than the presenting complaint that is the focus of the patient’s attention. The literature can only be described as depressing on every psychological, physiological and musculoskeletal parameter. When assessing these patients, it is most important to obtain a good rapport in a nonjudgemental and supportive fashion, particularly as the goal is to direct the patient to improved lifestyle choices.