Reporter was commissioned to write this in-depth article.

We're all well aware of the frightening ways in which obesity threatens our overall health. But one area often goes overlooked.
Being overweight can actually wreak havoc on your joints. If you're one of the 27 million Americans suffering from osteoarthritis (also known as degenerative joint disease), this may be something you know all too well.
The startling truth is that the number of people affected by this condition is increasing in direct correlation with the country’s obesity epidemic.
"Extra weight means increased stress on joints, especially weight-bearing joints, like the knees and the hips,” says John Meilahn, M.D., bariatric surgeon at Chestnut Hill Hospital.
Every pound of excess weight exerts about four pounds of extra pressure on the knees (Arthritis and Rheumatism, July 2005). 
“A person who is 100 pounds overweight, has about 400 pounds of extra pressure on his knees,” says Meilahn. “When you count the times you get up and down from a chair and the number of steps you take in a day, you can begin to understand the relationship between excess weight and damage in weight-bearing joints.” 
Osteoarthritis primarily affects the weight-bearing joints (think hips and knees), as well as the spine and feet. It stands to reason that excess weight can strain and damage these joints, causing pain and stiffness. In fact, health experts estimate that for every 10 pounds of excess body weight, the force of impact on the hips and knees increases 30 to 60 pounds with each step.
The most common symptom of osteoarthritis is pain in the affected joint. This pain especially rears its ugly head with repetitive use. In other words, regular activities like exercising, climbing stairs, or even bending can lead to painful flare-ups. Typical symptoms often include swelling, warmth and creaking of the affected joint.
Because excess body weight can play a huge role in the development of osteoarthritis, as well as other health problems such as high blood pressure, heart disease and pre-diabetes, it’s important to know if your current weight is a healthy one. One helpful tool in determining this is the BMI, or body mass index. (Click here to use a free BMI calculator.)
“The BMI guidelines are a relatively accurate estimate of an individual’s body fat, and related health risks,” says Meilahn. 
Knowing your number gives you more information and insight into your risk factors for various health problems ranging from diabetes to high blood pressure to high cholesterol. It also helps determine whether or not you're at a healthy weight.
For some individuals, weight loss surgery can be a successful, positive treatment option.