The medical diagnosis for obesity is based on body mass index or BMI. The BMI is equal to a person's weight divided by height. The calculations are done in metric. There's a web site that will help you find out your BMI easily: http://nhlbisupport.com/bmi/bmicalc.htm.
Anyone with a BMI less than (or equal to) 27 is within normal limits (not overweight). Between 27 and 30 is overweight. Between 30 and 40 is obese. Over 40 is
morbidly obese. Morbid is a word used to describe disease. Morbid obesity has been linked to many diseases such as diabetes, heart attacks, and strokes.
Stomach or gastric stapling (bypass) is becoming more popular as a treatment for morbid obesity. Many of the patients having this operation have been unable to lose weight successfully in any way. Not everyone is eligible for this surgery.
Your wife will need to have a doctor examine her and evaluate her potential for weight loss with this kind of treatment. It may be a good option. With weight loss there can be relief from painful knee symptoms when the stress and pressure of added weight is removed from the joint.