Knee Cartilage Loss Linked to Being Overweight

< Jul. 15, 2009 > -- According to a new report, being overweight or obese can cause rapid deterioration of the cartilage in the knee, leading to osteoarthritis - yet another reason for people to maintain a healthy body weight.

Obesity, among other factors, is strongly associated with an increased risk of rapid cartilage loss, according to the study published in the medical journal Radiology.

Osteoarthritis is the most common form of arthritis, affecting 27 million Americans, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). In osteoarthritis, the cartilage breaks down and can completely wear away in severe cases, leaving the joint without a cushion. The bones rub together, causing further damage, significant pain, and loss of mobility.

Osteoarthritis usually progresses slowly, but some patients experience a more rapid progression. This is the first study to connect obesity with fast progression of the disease and cartilage loss.

"We have isolated demographic and MRI-based risk factors for progressive cartilage loss," says Dr. Frank W. Roemer, the lead author of the study and adjunct associate professor at Boston University and co-director of the Quantitative Imaging Center at the Department of Radiology at Boston University School of Medicine. "Increased baseline body mass index (BMI) was the only non-MRI-based predictor identified," he adds.

Cartilage Loss Studied

The researchers recruited 336 patients from a major osteoarthritis study. All were overweight and at risk of osteoarthritis, but had minimal or no loss of cartilage in their knees.

During 30 months of follow-up, 20.2 percent of the patients showed a slow loss of knee cartilage and 5.8 percent had rapid cartilage loss, the study found.

The main risk factors for cartilage loss were pre-existing cartilage damage, being overweight or obese, tears or other injury to the cartilage at the knee joint (meniscus), and severe lesions seen on an MRI. Other factors included inflammation of the membrane lining the joints and abnormal build-up of fluid in the joint, according to the report.

Dr. Roemer's team found that being overweight was associated with rapid cartilage loss. In fact, for every one-unit increase in body mass index, the chances of rapid cartilage loss increased 11 percent.

Being Overweight a Primary Factor

The researchers say that the association between obesity and rapid cartilage loss remained even after taking into account age, gender, and ethnic background.

"[Osteoarthritis] is a disease without treatment at present other than symptomatic - mostly pain therapy and surgical total joint replacement," says Dr. Roemer.

"We know that weight loss is probably the most important factor to slow disease progression," Dr. Roemer continues. "Additional studies will have to show if other measures, such as vitamins or targeted treatment of bone marrow lesions, will help to slow progression," he says.

"Osteoarthritis is the most common musculoskeletal disorder with major health and socioeconomic impact in our aging society," adds Dr. Roemer.

Weight Control is Important

Dr. Sean Scully, a professor of orthopedics at the University of Miami Miller School of Medicine in Florida, agrees that the danger of developing osteoarthritis is another reason to control weight.

"Don't let yourself get heavy," Dr. Scully says. "This study shows a direct correlation - people who are heavy are the ones that are getting worse," he says.

Keeping your weight down - through diet and exercise or weight-loss surgery - could prevent the need for knee-replacement surgery, he adds.

Always consult your physician for more information.

More About Osteoarthritis

Osteoarthritis, the most common form of arthritis, is a chronic, degenerative, joint disease that affects mostly middle-aged and older adults. Osteoarthritis is characterized by the breakdown of joint cartilage and adjacent bone in the neck, lower back, knees, hips, and/or fingers.

The disease is also known as degenerative arthritis or degenerative joint disease.

Osteoarthritis can be classified as primary or secondary. Primary osteoarthritis has an unknown cause, while secondary osteoarthritis is caused by another disease, infection, injury, or deformity.

Osteoarthritis is characterized by the breakdown of cartilage in the joint and adjacent bone. As the cartilage wears down, the bone ends may thicken, forming bony growths or spurs that interfere with joint movement. In addition, bits of bone and cartilage may float in the joint space and fluid-filled cysts may form in the bone, limiting joint movement.

Several risk factors are associated with osteoarthritis, including the following:

• heredity
  Slight joint defects or double-jointedness (laxity) and genetic defects may contribute to the development of osteoarthritis.
• obesity
  Excessive weight can put undue stress on such joints as the knees over time.
• injury/overuse
  Significant injury to a joint, such as the knee, can later result in osteoarthritis. Injury may also result from repeated overuse or misuse over a period of time.

The most common symptom of osteoarthritis is pain after overuse of a joint or prolonged inactivity of a joint. The most common joints affected by osteoarthritis include the hips, knees, fingers, feet, and spine. Symptoms of osteoarthritis usually develop slowly over many years.

The following are the most common symptoms of osteoarthritis. However each individual may experience symptoms differently. Symptoms may include:

• joint pain
• joint stiffness, especially after sleeping or inactivity
• limited joint movement as the disease progresses
• grating of joints when moved (in more advanced stages of osteoarthritis) as the cartilage wears away
• back pain
• numbness
• weakness in an arm or leg (in more advanced stages)

The symptoms of osteoarthritis may resemble other medical conditions or problems. Always consult your physician for a diagnosis.

Always consult your physician for more information.