By Dr Ananya Mandal, MD
Obesity affects nearly a third of the population in developed nations like the United States and the United Kingdom. It is a rising epidemic that is one of the major public health problems.
According to the World Health Organization obesity affects an estimated 1 billion people worldwide. This means 34 million US adults are obese, and 13 million of these are morbidly or severely obese.
Obesity is associated with numerous health conditions including several conditions that affect the musculoskeletal system. These disorders have the power to severely impair mobility and joint pain.
As the population has aged and become heavier, arthritis, especially osteoarthritis has become one of the leading causes of disability worldwide. Ten percent of the European population over age 65 show X ray evidence of osteoarthritis and half of these show symptoms of the condition.
Among Americans over 55 years of age, 2.4% of the population have disabling pain from knee osteoarthritis and by age 65 twice as many women as men in the same age range may be affected.
Obesity and types of arthritis
Obesity for example increases the risk of knee osteoarthritis but has a lesser effect on disease progression. In addition there is a weaker association with hip and hand osteoarthritis as well.
Osteoarthritis is a painful degenerative condition that can affect one or more joints. The weight-bearing joints including spine, hip, knee and ankle are often involved in the disease process. Obesity mainly affects the knees due to the increased weight burden that it provides on the knee joints.
Some initial studies have also linked obesity with an increased risk of rheumatoid arthritis. Obesity is also strongly associated with high blood levels and joint levels of uric acid and gouty arthritis.
Association between obesity and arthritis
Obesity as well as several other factors in the lifestyle is associated with osteoarthritis. Some of these include joint activity, lack of exercise, muscle weakness, and joint injury. Of these lack of exercise is also associated with obesity and muscle weakness is common in obesity as well.
The basic pathology behind obesity and knee osteoarthritis is the weight burden that has to be borne by the knees in an obese and overweight individual.
While walking or bearing the weight on a single leg with each step while walking, a force of 3 to 6 times that of body weight is transmitted across the knee joint. Similarly the force exerted across the hip is 3 times that of body weight.
These forces are increased several times over during high-impact activities. In fact only 10 pounds overweight can increase the force on the knee by 30-60 pounds with each step.
In addition there are excessive fat tissues that produce hormones and other factors that affect the articular or joint cartilage metabolism and cause inflammation of the joints giving rise to joint pathology. Leptin is one of the hormones associated with obesity induced knee osteoarthritis.
Weight loss benefits for arthritis patients
Weight reduction has shown benefits in improvement of symptoms of both osteoarthritis and gout.
Obesity at a young age has been strongly associated with development of osteoarthritis. Thus preventive public health strategies aimed at lowering the incidence of obesity are of most importance in preventing arthritis and its complications.
Bariatric surgeries are weight loss surgeries performed in morbidly obese patients to help them lose weight. Bariatric procedures have shown to not only decrease obesity but also decrease osteoarthritis incidence and symptoms.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)
Last Updated: Apr 8, 2013