Obesity And Osteoarthritis: Is There A Connection?
Osteoarthritis is a degenerative joint disease that affects nearly 27 million residents of the United States, making it the most common form of arthritis [1]. Joint pain is the foremost symptom of osteoarthritis (OA) and results from the loss of articular cartilage, the connective tissue whose presence cushions and lubricates the joint. Affected joints are mostly in the knees, hips, and hands. At the onset of the disease, pain occurs when the joint is under stress. As OA progresses, pain is felt even during sleep.
Options for OA therapy are either surgical or non-surgical in nature. Surgery for OA consists of joint replacement and is generally utilized on individuals whose cartilage has deteriorated to the point that other therapies no longer provide relief. However, obese persons are often ineligible for this type of surgery due to increased surgical dangers associated with their excess weight.
Pharmacological treatment of OA may include the use of analgesic painkillers such as Tylenol or ibuprofen. NSAID’s (non-steroidal anti-inflammatory drugs) such as Aleve, Advil and Orudis are also prescribed. However, medications carry the risk of serious side effects including liver damage and gastro-intestinal bleeding, which may result in premature death.
Alternative treatment of OA includes changes to lifestyle and diet and a course of acupuncture as well as ongoing physical therapy.
Natural pain relief formulas have become immensely popular as a treatment of OA. While enthusiasm was initially based on anecdotal evidence, the GAIT, or Glucosamine/Chondroitin Arthritis Intervention Trial, carried promising implications for the effective use of glucosamine sulphate and chondroitin, which are currently taken as dietary supplements by over 5 million Americans.
Does obesity encourage osteoarthritis?
Obesity has become a global epidemic, causing excess disease and premature death. The CDC (Centers for Disease Control) estimates that one-third of American adults are obese.
Studies have shown that obese individuals are at increased risk of developing an array of musculoskeletal disorders that result in joint pain and locomotor disability, including osteoarthritis. It is therefore not surprising that as rates of obesity have increased worldwide, diagnoses of osteoarthritis have also risen.
A 2001 survey of 7500 Australians showed that increased BMI (body mass index) resulted in twice the likelihood of affliction with osteoarthritis, regardless of other contributing factors such as sex, age and socioeconomic status.
Obesity and OA of the knee
All across the world, survey after survey has demonstrated a linear trend between increased body mass index (BMI, an index of obesity) and knee OA.
A 2006 Scottish survey of 858 people demonstrated that knee and hip pain was doubled in obese participants.
The HANES 1 survey (Health and Nutrition Examination Survey), which was sponsored by the National Center for Health Statistics and conducted between 1971 and 1975, analyzed data from 5,193 Americans. The findings showed that for every 5-unit increase in BMI, there was double the risk of developing knee OA [2].
A cohort study based on the Framingham Heart Study took data collected between 1948 and 1951 from 1,420 participants (whose average age was 37) and followed up between 1983 and 1985, evaluating the participants (whose average age was then 73 years) for knee arthritis. The findings from this UK study showed that being overweight at the mean age of 37 was a strong indicator for developing OA of the knee in later life [3].
The UK’s 1999 Chingford Study took data over a period of 4 years from 840 middle aged women. The study showed that the risk of developing osteophytes (bony spurs that appear in arthritis-damaged joints) was twice as likely in women with a BMI higher than 26.4 (a person with BMI above 25 is considered overweight) as compared to women with a BMI lower than 23.4.
When it comes to OA of the knee, one plausible explanation is that the excess force exerted upon the knee joint by the additional weight could cause the breakdown of cartilage, leading to osteoarthritis.
Obesity and OA of the hip
The force exerted on the hip joint is lighter and more evenly distributed than on the knees. Although the correlation between obesity and OA of the hip is not as pronounced as that between obesity and OA of the knee, obese individuals still have a higher than normal risk of developing hip osteoarthritis [4].
Data gathered from the Nurses’ Health Study shows that higher BMI significantly increased the likelihood of undergoing a total hip replacement caused by OA. Part of the risk appeared to be connected to being overweight early in life.
Extensive cohort studies have also found a positive connection between BMI and OA of the hip. The Norwegian Flugsrud study of 1.2 million individuals showed that the likelihood of undergoing hip replacement later in life was higher by 3.4 times among men with a BMI over 32 as compared to men whose BMI was under 21.
Obesity and OA of the hand
Obese individuals appear to have a higher prevalence of osteoarthritis of the hand than persons who are not overweight. This fact implies that the mechanical stress that excess weight exerts upon the joints of obese individuals is not the only causal factor of OA.
Since hands are not weight-bearing joints, the stress on hand joints experienced by obese persons does not exceed the stress felt by persons of normal weight. Scientists believe that this finding implies a metabolic factor associated with obesity that accelerates cartilage breakdown. Adipose (fatty) tissue could cause release of an endocrine factor particularly in postmenopausal women that could affect the joints.
Which comes first — obesity or OA?
A causality question is raised by the obesity-OA link. One hypothesis is that individuals with osteoarthritis of the knee become more sedentary, due to the pain associated with movement, and subsequently gain excess weight.
However, OA affliction of non weight-bearing joints (elbow, hands, etc) suggests that humoral and metabolic factors that are secreted by the adipose tissue of obese individuals may play a role in the disease, complicating determinations of causality.
Conclusion
Obesity increases the risk of developing osteoarthritis of the knee, hip and hand. Knee OA is the most prevalent type of arthritis found in obese people, most probably due to the excess force exerted upon the knee joints. Weight reduction is an important part of any strategy to successfully treat osteoarthritis and is especially effective at reducing symptoms associated with OA of the knees.
[Matthew Papa, PhD, is a biology researcher who has worked for more than 10 years in the medical research field. He keeps abreast of the current scientific research on obesity treatment, diets and weight loss programs. Matthew considers it a privilege to write for the RagBlog. In his own blog, he offers a Diet to Go promo code and Bistro MD coupon code discounts, two successful meal replacement programs.]
References
1. Am J Manag Care. 2009 Sep;15(8 Suppl):S230-5. The economic burden of osteoarthritis. Bitton R.
2. Evidence for an association with overweight, race, and physical demands of work. Factors associated with osteoarthritis of the knee in the first national Health and Nutrition Examination Survey (HANES I). Anderson et al. Am J Epidemiol 1988;128:179–89
3. Obesity and knee osteoarthritis. The Framingham Study. Felson DT, et al. Ann Intern Med 1988;109:18–24
4. BMI Independently Predicts Younger Age at Hip and Knee Replacement. Gandhi R, Wasserstein D, Razak F, Davey JR, Mahomed NN. Obesity (Silver Spring). 2010 Apr 8.
