Obese Are Three Times as Likely to Need a Hip or Knee Replacement

Rate of knee replacement procedures more than doubled among women aged 45 to 54

August 17, 2005 – Patients who underwent hip and knee replacements in 2003-2004 had a significantly higher rate of obesity compared to population norms, according to a new annual report by the Canadian Institute for Health Information (CIHI). Nearly half of those getting knee and hip replacements were considered obese; this is higher than the rate of obesity seen among the Canadian population in general. For those having a knee replacement, the likelihood of being either obese or overweight was greater than for those having a hip replacement. Nearly 9 in 10 knee replacement patients in 2003–2004 were overweight or obese, compared to just over 7 in 10 patients who had a hip replacement.

“There is a strong link between obesity and an increased risk of osteoarthritis, which is a key diagnosis in joint replacement surgery,” says Margaret Keresteci, Manager of Clinical Registries at CIHI. “If we reduce the prevalence of arthritis by addressing obesity, we could decrease the number of joint replacements required. This could in turn improve the quality of life for Canadians and at the same time could potentially shorten waiting times for these procedures.”

Body mass index (BMI) was available for just over 17,000 patients, accounting for 65% of hip and knee replacement procedures reported in the study. For those who had a joint replacement in 2003–2004, 46% were classified as “obese” (BMI of 30.0 or higher), compared to the Canadian population norm of 23% in this category. Those considered “overweight” (BMI 25.0 to 29.9) made up roughly the same percentage as the Canadian population norm, with 35% and 36%, respectively. While only 18% of joint replacement patients were considered to have “acceptable” weights (BMI 18.5 to 24.9), the Canadian population norm was 39%.

After adjustment was made for the effects of age and gender, people who were obese were three times more likely to get hipor knee joint replacements, compared to people with an acceptable weight. People who were overweightwere twice as likely to have a joint replacement.

“Our data tell us that being obese or overweight not only increases the likelihood of needing a joint replacement, but it also has a negative impact on how well a patient recovers and how long a patient remains in hospital following surgery,” Keresteci explains. “Being obese or overweight can also increase the necessity for repeat surgeries—modifications to or replacements of the artificial joints—because the extra weight adds more wear and tear on the prostheses.”

According to Total Hip and Total Knee Replacements in Canada, the Canadian Joint Replacement Registry (CJRR) 2005 report, there were nearly 50,000 hospitalizations for hip and knee replacements in 2002–2003, representing a more than 50% increase in eight years.

Sex, Age and Joint Replacements

Women were more likely to have a total hip replacement procedure compared to men in 2002–2003, making up 59% of patients. Similarly, women received more knee replacements, comprising 61% of patients. Male patients were more likely to be overweight or obese (85% combined) compared to female patients (79% combined).

Seniors made up the majority of those who underwent hip and knee replacements in 2002–2003 (66% and 69%, respectively). Only 5% of patients who had a hip replacement and 1% of those who had a knee replacement were younger than 45. However, the rate of knee replacement procedures has doubled among men aged 45 to 54 (99% increase) and more than doubled among females in that age group (133% increase) in the past decade.

Joint replacement patients aged 45 to 84 were more likely to be obese or overweight (82%), as compared to the other two age groups (65% for those under the age of 45 and 57% for those aged 85 and over).

The proportion of Canadian children who are overweight and obese has more than doubled in the last 20 years. If this trend continues, upon reaching adulthood these individuals may be even more likely to develop arthritis and require joint replacement surgery.

“When we look across the country, we see that obesity rates vary,” says Elizabeth Gyorfi-Dyke, Director of CIHI’s Canadian Population Health Initiative. “By looking at what programs and policies work, this information can be used to encourage healthy weights in Canada.”

Provincial Obesity Rates Linked to Number of Hip and Knee Replacement Surgeries

Saskatchewan had the highest age-standardized rate for hip replacements, with 81 per 100,000 population, followed by Alberta, with 75. The lowest rates per 100,000 population were recorded by Quebec, with 42, and Newfoundland and Labrador, with a rate of 50. As for revisions (or altering the replacement), Prince Edward Island reported the highest percentage of revisions, with 23%, while Saskatchewan reported the lowest percentage, with 8%.

For knee replacements, Manitoba and Nova Scotia reported the highest age-standardized rates, with 98 per 100,000 population. Quebec had the lowest rate, with 44 per 100,000 population, while Newfoundland and Labrador had the second lowest rate for knee replacements, with 49. P.E.I. again reported the highest percentage of revisions, with 13%, and Newfoundland and Labrador had the lowest percentage of revisions, with 6%.

The provincial rates for obesity are generally in alignment with varying rates for joint replacement surgery. The provinces that reported the highest rates for hip replacements (Saskatchewan and Alberta) and for knee replacements (Manitoba and Nova Scotia) also have reported obesity rates that are higher than the national average of 23%. Mirroring the same relationship between BMI and joint replacement surgery, British Columbia and Quebec consistently had among the lowest rates for both surgeries and similarly have reported obesity rates that are lower than the national average.

Across the country, the prevalence of obesity has doubled among Canadian adults over the last two decades. Parallel with this, the joint replacement data show large proportions of obese and overweight patients undergoing joint replacement procedures.

Canadian Joint Replacement Registry

The CJRR, managed by the Canadian Institute for Health Information, provides comprehensive data on total hip and total knee replacements performed in Canada. Data are collected on a voluntary basis from patients, with the majority of patients participating. A pan-Canadian advisory committee, whose members include orthopaedic surgeons, consumers and representatives from the Canadian Orthopaedic Association, the Canadian Orthopaedic Foundation and the Arthritis Society, provides advice to CIHI on the registry’s development and implementation. At present, 510 orthopaedic surgeons are participating in the registry.

Canadian Population Health Initiative (CPHI)

The Canadian Population Health Initiative is part of the Canadian Institute for Health Information (CIHI). CPHI supports research to advance knowledge on the determinants of health in Canada and to develop policy options to improve population health and reduce health inequalities. CPHI is releasing a report on healthy weights in January 2006, which will examine the environmental and social structures that may facilitate or discourage healthy weights.

Canadian Institute for Health Information

The Canadian Institute for Health Information (CIHI) is an independent, pan-Canadian, not-for-profit organization working to improve the health of Canadians and the health care system by providing quality health information. CIHI’s mandate, as established by Canada’s health ministers, is to coordinate the development and maintenance of a common approach to health information for Canada. To this end, CIHI is responsible for providing accurate and timely information that is needed to establish sound health policies, manage the Canadian health system effectively and create public awareness of factors affecting good health.

About CIHI

The Canadian Institute for Health Information (CIHI) is one of Canada’s premiere sources of high quality, reliable and timely health information. An independent, Canadian, not-for-profit organization, CIHI is a focal point for collaboration among major health players—from provincial governments, regional health authorities and hospitals to the federal government, researchers and associations representing health care professionals. For more information, visit www.cihi.ca.