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United States maps demonstrating, by state, the percentage of adults who were obese (ie, body mass index ≥30 kg/m2) in the years 1991 and 2010. The change in this 20-year period is dramatic. (Reproduced with permission from Centers for Disease Control and Prevention: Adult Obesity Facts. Atlanta, Georgia, Centers for Disease Control and Prevention, 2012. http://www.cdc.gov/obesity/data/adult.html.) View larger PDF of this image.

AAOS Now

Published 3/1/2013
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Peter Pollack

Is There a Systemic Link between Obesity and OA?

Studies suggest that wear and tear is only one factor

“Obesity is a topic that I believe is relevant to all orthopaedic surgeons,” explains Jonathan T. Bravman, MD, of the department of orthopaedics, CU Sports Medicine, University of Colorado School of Medicine. “We’re seeing increasing obesity rates, which has a strong effect on how we treat musculoskeletal disease.”

Recent estimates for all adults in the United States indicate that nearly 68 percent are overweight—and more than a third could be classified as obese. According to the Centers for Disease Control and Prevention (CDC), medical costs associated with obesity were estimated at $147 billion in 2008; the medical costs for people who are obese were $1,429 higher than those of normal weight.

Dr. Bravman and his coauthor, Ryan C. Koonce, MD, of the department of orthopaedic surgery at Skagit Regional Clinics in Mount Vernon, Wash., make the case that the relationship between obesity and osteoarthritis (OA) is not simply one of biomechanical cause and effect, but has a hormonal component as well. Their review article, “Obesity and Osteoarthritis: More Than Just Wear and Tear,” appears in the March issue of the Journal of the AAOS.

An endocrine organ
Drs. Koonce and Bravman explain that an intuitive biomechanical relationship exists between obesity and OA, in which increased loads on articular cartilage cause subsequent wear and cartilage breakdown. In addition, evidence of a systemic relationship between lipid metabolism and OA has been found. This systemic relationship has been widely reported in the general medical literature but is rarely found in orthopaedic journals. Orthopaedic surgeons, they say, should be aware of obesity’s systemic implications with respect to OA and should take that systemic factor into account when counseling patients.

“Studies show that even in non–weight-bearing joints such as the hand, the presence of osteoarthritis is increased in obese patients, compared to non-obese patients,” says Dr. Koonce. “In those non–weight-bearing joints, loading isn’t likely to be a factor in the development of OA, so seeking a systemic cause makes sense.”

Drs. Koonce and Bravman write that, although OA has been often labeled as “wear-and-tear” arthritis, OA actually has an inflammatory component, which is attributed to the presence of excess adipose tissue.

“Traditionally, we consider adipose tissue to be an energy store,” says Dr. Koonce. “But adipose tissue is known to secrete adipokines—pro-inflammatory cytokines that target different organs. One of the targets seems to be articular cartilage.”

“We’re now starting to put the puzzle pieces together to get a better idea of adipose tissue as a really freely functioning endocrine organ, one that’s acting at the cellular level in concert with mechanical, alignment-based factors,” agrees Dr. Bravman. “The literature is becoming replete with evidence that the perception of musculoskeletal pain, weakness, and strength-to-weight ratio are somewhat independent of joint or cartilage health. The medical community is starting to build a unified theory that combines the sophistication we’re discovering at the cellular level with our understanding of alignment and increased joint loading.”

Weight loss as a primary treatment
With this in mind, Drs. Koonce and Bravman argue that weight loss should be offered as a primary treatment option for persons with musculoskeletal pain and OA. They encourage their orthopaedic colleagues to work with other healthcare providers as part of a comprehensive plan to help patients lose weight.

“It’s important for surgeons to understand that excess adipose tissue not only increases the risk of arthritis,” says Dr. Koonce, “but likely increases the symptoms of arthritis. So weight loss in the obese population may help not only to prevent osteoarthritis, but also to control pain and symptoms that go along with it.”

Although obesity can be a sensitive subject for patients and one that many orthopaedists may feel uncomfortable discussing, Dr. Bravman thinks that most patients have enough self-awareness to understand their general health situation. Many, he says, are even grateful to work with a healthcare professional willing to give them the push they may need to lose weight.

“I’ve found patients typically appreciate it,” he says. “More often than not, patients have the same goals as we do. They would love to lose weight. They would love to feel better. And, as orthopaedic surgeons, we have at our disposal resources and people to whom we can refer them. We can help guide them with counseling, support, and assistance in achieving their goals.

“Obesity is a metabolic phenomenon and a modifiable risk factor,” he continues. “Addressing obesity is a legitimate treatment option for OA, and something we should consider for our overweight and obese patients with musculoskeletal pain.”

“Obesity is a worldwide epidemic,” notes Dr. Koonce. “It’s probably undertreated by all physicians, including orthopaedic surgeons. A report from 2010 that we didn’t include in the paper estimated that the yearly economic burden of obesity for the United States was in excess of $215 billion. This is a major problem that I think we’re just starting to recognize and treat, and we have a long way to go.”

Disclosure information: Dr. Bravman—Stryker; Dr. Koonce—no conflicts.

Peter Pollack is a staff writer for AAOS Now. He can be contacted at ppollack@aaos.org

Bottom Line

  • Wear and tear may be only one factor in a complex interaction between obesity and OA.
  • Adipose tissue can act as an endocrine organ, increasing inflammation in articular cartilage.
  • Weight loss should be considered a primary treatment option for overweight patients with OA and musculoskeletal pain.