Arthritis Research - The Largest Subset of All Musculoskeletal Disorders

Arthritis is classified by researchers and clinicians under the broad category of musculoskeletal (MSK) disorders and constitutes its largest sub-set (about 60 per cent of all cases). Of the more than 100 distinct conditions that are collectively called "arthritis," osteoarthritis (OA) is the most common, affecting one in 10 in the general population - about 3 million Canadians. By contrast, rheumatoid arthritis (RA), the next most common type of arthritis, affects around one in 100 Canadians (about 300,000 people, mostly women). While the degenerative course of OA often unfolds over decades, the systemic inflammation of RA can destroy many joints in just a short span of years.

At present, there is no cure available for either degenerative or inflammatory arthritis. Once cartilage and bone are severely damaged by arthritis, the only effective therapy is orthopaedic surgery to repair or replace a joint.

Although osteoarthritis follows a slower more seemingly benign course than RA, its impact on quality of life shouldn't be underestimated. OA is so prevalent that, even though only a minority experience disabling symptoms, the resulting burden of illness is enormous. For every case of significantly disabling RA, there are seven cases of OA of equal severity.

Chronic pain and reduced mobility and function are the most common outcomes of long-term arthritis, a combination of factors that lead to just the sort of inactive life and loss of independence widely recognized as predisposing conditions for depression, cardiovascular disease and Type II diabetes, as well as other sorts of chronic ill-health. In short, arthritis is very often the precipitating event that transforms a robust constitution into frail health. Over all, arthritis disables about 600,000 people - a population equivalent to a mid-sized Canadian city.

Of all the known risk factors for OA, age is the most important. The prevalence of osteoarthritis (as well as MSK disorders in general) increases in direct correspondence with age. Indeed, a common perception is that arthritis is exclusively a disease of old age - understandable, given the high prevalence, but untrue. In reality, arthritis is a disease that affects young and old alike. Recent population studies indicate that people of working age (20-64) comprise close to 60 per cent of Canadians with arthritis.

Arthritis (mostly osteoarthritis) has a severe impact on people's careers and long-term expectations. For all age groups, arthritis disables two to three times more workers than all other chronic conditions. More than 30 per cent of Canadians with arthritis aged 45-55 are no longer in the labour force. And the disability ratio climbs to more than one in two for working Canadians with arthritis from 55-64 years of age. Not surprisingly, poverty is another common outcome of arthritis.

OA Consensus Conference Provides Unique Insights

By the end of this decade, more than half of the nearly 10 million Canadians who comprise the post-war "baby boom" generation (1947-67) will be aged 50 or more. Epidemiologists predict approximately 100,000 new cases of arthritis per year for at least the next 30 years - around half of which, they project, will be among Canada's mature workforce.

Even though the course of OA takes many years to develop, the need for innovative public-health strategies and disease-modifying therapies for OA couldn't be more urgent, if Canada is to effectively manage the upcoming surge in arthritis. Responding to the crisis, IMHA in conjunction with The Arthritis Society (TAS) and the Canadian Arthritis Network (CAN), convened an international Osteoarthritis Consensus Conference in April 2002.

Delegates and speakers ranged from basic scientists, specialist clinicians, and epidemiologists to individuals with arthritis. The following represents some of their many observations:

  • Osteoarthritis affects all of a joint's tissues, not just cartilage. OA might be a systemic disease; but it's certainly not a natural part of aging.
  • Osteoarthritis often follows different courses for different joints, sometimes characterized by bony outgrowth and other times by soft-tissue inflammation. Distinct sets of genes are activated by osteoarthritis depending on the affected joint.
  • Osteoarthritis results from the ineffective and/or incomplete ability of a joint, and to repair and regenerate in response to injury. Joint injury increases the risk of OA tenfold.
  • Osteoarthritis and pain are not synonymous. Some people who have extensive cartilage erosion experience little or no pain; whereas others with only mild damage are in extreme, unremitting pain. Clinicians should treat chronic pain early and aggressively to avoid permanent remodeling of the brain's neural pain-pathways.
  • Osteoarthritis is confirmed diagnostically after cartilage damage is detected by X-ray, which is too late to be truly helpful. Scientists need to have a better understanding of early cartilage changes leading to OA (before the cartilage degrades), and clinicians need to have cost-effective methods of detecting them.
  • Osteoarthritis offers many potential therapeutic targets - ranging from enzymes to cytokines to cell receptors to DNA transcription factors - that could in theory be manipulated to actually modify the course of the disease.

As might be expected, the OA consensus conference not only provided unique insights into this most prevalent type of arthritis, it also raised many, many unanswered questions, such as: Is OA becoming more common and starting earlier in life? What are the determinants of OA-related disability? Why is it that most people with OA don't need a hip or knee replacement even though many still do? In what way does the cartilage structure weaken before it crumbles, and what agents cause it to weaken? What are the best ways to treat chronic pain? And are there molecules in urine or blood that could be used to accurately measure changes in cartilage metabolism before the damage is done?

These questions, among others, will help establish the priorities and frames of reference from which IMHA will develop its OA research agenda.

Strategic Multi-disciplinary Research Required

Clearly both degenerative and inflammatory arthritis are extremely complex disorders that require integrated, multidisciplinary research to find useful solutions to a host of unanswered questions. And the Institute, with its emphasis on musculoskeletal health, provides the ideal venue to braid together different strands of inquiry into a comprehensive effort to move arthritis research forward. Among other things, the scientists working in IMHA's other focus areas complement the arthritis-research community's expertise in cartilage metabolism and chronic inflammation.

Oral-health researchers are pioneers in pain management and biomaterials for implants. Basic-science knowledge about how muscle tissue behaves at the cellular and molecular levels can be quickly translated into effective applications in the musculoskeletal (MSK) rehab clinic. Skin inflammation and scar tissue formation provide useful laboratory models for some of the disease processes associated with inflammatory types of arthritis, such as RA and lupus. Complete understanding of the biological regulation of bone growth and bone absorption would be an enormous step forward on the path to possible new therapies.

Arthritis already poses immense challenges to Canada's health-care system; and as our population ages, the incidence of arthritis must surely rise. Peer-reviewed, multi-disciplinary, strategic research provides the best option for offsetting the impact of arthritis on Canadian society.

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