Weight loss can help reduce knee pain from arthritis

Nanci Hellmich | USA TODAY

If you're one of the millions of people suffering from knee pain, take heart. Heavy adults with knee osteoarthritis who lose 10% of their starting weight can significantly reduce their knee pain, walk faster and improve their mobility, a new study shows.

About 250 million people worldwide have knee osteoarthritis, which is the leading cause of disability in older adults, says lead author Stephen Messier, a professor of health and exercise science at Wake Forest University in Winston-Salem, N.C. It can lead to loss of mobility and diminished quality of life, he says. "Mobility is critical to being able to grow old independently."

Osteoarthritis is a chronic condition characterized by the breakdown of the joint's cartilage, according to the Arthritis Foundation. Cartilage is the part of the joint that cushions the ends of the bones and allows easy movement of joints. The breakdown of cartilage causes the bones to rub against each other, causing stiffness, pain and loss of movement in the joint.

Obesity is a major risk factor for knee osteoarthritis, Messier says. There are two possible pathways to knee osteoarthritis. One is biomechanical, which means the load on the joint has an effect on the knee, and the other is an increase in inflammation, which can affect muscle function and sensitivity to nerve endings, which increases pain, he says. "What we found was both pathways were affected by weight loss."

A 10% weight loss "can help people with knee osteoarthritis who are overweight or obese maintain their independence and have a good quality of life for the long term," he says.

Messier and colleagues recruited 454 overweight and obese adults with osteoarthritis in their knees. They reported having pain in their knees most days of the week. All were 55 or older and considered sedentary. For the 18-month study, participants were assigned to one of three groups: a diet-and-exercise plan; a diet-only plan or an exercise-only program.

The exercise group worked out for one hour a day three days a week for 18 months, doing mild to moderate-intensity walking and strength training.The women following the diet programs followed a balanced, calorie-restricted diet with at least 1,100 calories a day; men consumed at least 1,200 calories a day. Diets were tailored to the individuals.

At the beginning of the study, dieters could choose to consume up to two 300-calorie meal-replacement shakes a day (or other meal replacement such as a protein bar or calorie-controlled prepared meal) and one meal that was 500 to 750 calories and low in fat. After about six months, dieters had the option to gradually stop using meal replacements, replacing them with other healthy, low-calorie foods.

The diet-and-exercise group followed both the meal plan and exercise program. The diet group followed the calorie-restricted eating plan.

Findings reported in Wednesday's issue of JAMA:

• The participants in the diet-and-exercise program lost an average of about 23 pounds (about 11.4% of their starting weight) in 18 months; those who just dieted lost 19.6 pounds (9.5%); those who just exercised lost about four pounds (2%). Most of the weight was dropped in the first nine months on the program with a continued, more gradual reduction through the 18 months with no weight regain in either group.

• Those in the diet-and-exercise group had less knee pain, walked faster and felt better about performing the activities of daily living such as walking up stairs and getting out of chairs than those in the exercise group.

• People in the diet-and-exercise group who completed the study reported a 51% reduction in pain; compared with a 25% pain reduction for people who just followed the diet and a 28% reduction in pain for those who just exercised.

• Everyone increased their walking speed, but the participants in the diet-and-exercise group increased it the most.

• Both diet groups had greater reductions in Interleukin 6 levels — a measure of inflammation — than the exercise group.

• The weight loss in the diet intervention group helped to reduce load on the knee by 45 pounds per step. When you walk you exert about three times your body weight on your knees, so people who lost weight were able to decrease that load, Messier says.

The more weight people lost, the greater the improvements, he says. Those who lost more than 10% of their starting weight had less pain, better mobility, decreased joint load and decreased inflammation than those who lost less, Messier says.

Increasing walking speed is a major accomplishment, he says. After age 30, people often lose 1% to 2% of their walking speed for each decade of life, he says. After age 63, their speed decreases by 12% to 16% per decade, but participants in this study increased their walking speed at an age when most older adults are decreasing it, he says.

There is a lot of room for improvement in treatments for knee osteoarthritis, Messier says. In patients treated with medications, only about half report a 30% reduction in pain. "We are not saying weight loss and exercise should replace medications," but doctors should recommend that overweight patients with knee osteoarthritis lose weight and exercise.

Rheumatologist David Felson, a professor of medicine and epidemiology at Boston University, says the study shows that "knee pain improves and function improves substantially more when patients both lose weight and exercise. The more we emphasize this, the more we can motivate people to accomplish it."

Weight loss and increased physical activity in patients with knee osteoarthritis could lead to decreased health care costs and fewer joint replacements in the future, says rheumatologist Patience White, a spokeswoman for the Arthritis Foundation. "Osteoarthritis is a huge public health problem that's going to grow considerably in the next 20 years because of obesity, lack of physical activity, the aging population and injuries. This epidemic is something we have to pay attention to and this study shows us ways to make a difference."

Some facts about osteoarthritis from the Arthritis Foundation (arthritis.org):

• An estimated 27 million people in the USA have osteoarthritis.

• Osteoarthritis most commonly occurs in the weight-bearing joints of the hips, knees and lower back. It also affects the neck, small finger joints, the base of the thumb and the big toe. It rarely affects other joints except when injury or stress is involved.

• Most treatment plans will include a combination of the following elements: exercise, weight control, joint protection, physical and occupational therapy and medications.

The most common signs and symptoms of osteoarthritis are:

• Joint soreness after periods of overuse or inactivity.

• Stiffness after periods of rest that goes away quickly when activity resumes.

• Morning stiffness, which usually lasts no more than 30 minutes.

• Pain caused by the weakening of muscles surrounding the joint due to inactivity.

• Joint pain is usually less in the morning and worse in the evening after a day's activity.

• Deterioration of coordination, posture and walking due to pain and stiffness.

Source: Arthritis Foundation (arthritis.org)