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The musculoskeletal system consists of bones, muscles, tendons, ligaments, joints, cartilage, and other connective tissue. These components all work together to provide form, stability, and movement to the human body. Diseases of the musculoskeletal system may result in the inability to walk, sit, or even breathe, and have a substantial impact on the health of Canadians. Musculoskeletal diseases are generally accompanied by pain (ranging from mild to severe), limitations in physical functioning, and fatigue. Activities of daily living, such as social and work commitments are often restricted. The functional and social limitations associated with musculoskeletal diseases often have emotional consequences as well, notably anxiety and depression.
This document presents health states that describe and classify the functional limitations associated with selected musculoskeletal conditions. The musculoskeletal conditions having the most impact on population health will be presented: back pain, repetitive strain injury (RSI), osteoarthritis (OA), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and fibromyalgia. Other musculoskeletal conditions that are more common yet have a comparatively low impact on functional health (e.g., gout) will not be presented.
Three health states are presented for back pain based on duration of the pain and location on the spine: acute neck (cervical) pain, acute low (lumbar) back pain, and chronic low back pain. The causes of back pain are generally biomechanical in nature, aggravated by improper lifting techniques or poor muscle tone. Back pain can also occur from inflammation in the spine, a particular trauma, or from another underlying medical condition. The description for chronic low back pain also applies to other conditions that have similar functional limitations, such as osteoarthritis of the spine, ankylosing spondylitis, degenerative disc disease, and repetitive strain injury of the back.
Repetitive strain injury (RSI) refers to a range of conditions caused by repetitive movements and force, awkward postures, and work-related hazards. RSI can result in functional limitations described as three health states—RSI of the hand, elbow, and shoulder—as well as the health state for chronic back pain. Occupational overuse syndrome can be considered a subset of RSI, since a substantial proportion of RSIs stem from work-related activities involving repetitive movements. However, we do not make a distinction between repetitive strain injuries and occupational overuse disorders because the consequences for functional health are similar, and are not necessarily the result of a work-related activity. Repetitive strain injury is not considered in the International Classification of Diseases—version 9 (ICD-9) coding,1 although common disorders that result from RSI have their own code (for example, Carpal Tunnel Syndrome is ICD-9 354.0).
Osteoarthritis (OA) is characterized by the breakdown of cartilage in a joint, and will be discussed here in terms of the most common areas affected: the hands and lower extremities (hip and knee). OA of the spine is also common; the associated functional limitations are presented in the health state for chronic back pain.
Rheumatoid arthritis (RA), a chronic disease in which the body’s immune system attacks healthy joint tissue rather than foreign cells, will also be discussed here. This disease is presented as three health states because RA has a waxing and waning pattern in which individuals tend to go through periods of more or less active inflammation; most individuals with RA have some degree of inflammation on an ongoing basis (chronic active inflammation), but experience periods when symptoms flare up (acute episodes). Additionally, due to the chronic, degenerative nature of the disease, we describe the typical health state following years of inflammation and damage to the joints (advanced damage). Remission is also possible, but we do not describe this health state because the disease is almost or completely inactive and therefore the functional limitations are negligible.
Systemic lupus erythematosus (SLE) is an autoimmune disease in which the immune system attacks the tissues and organs of the body. It is the most common type of lupus (70% of cases2) and affects approximately 15,000 Canadians,3 mostly women, often at young ages. Some individuals have a more limited form of the disease, such as subacute cutaneous lupus erythematosus, drug-induced lupus erythematosus, neonatal lupus (occurring in newborn babies of women with SLE), and discoid lupus (when only the skin is involved). These forms will not be described in this document. When the disease involves multiple parts of the body (beyond the skin), the condition is called systemic lupus erythematosus (SLE). SLE can also affect almost any internal organ in the body (brain, nerves, kidneys, lungs, heart, eyes, gut and bowels), often leading to severe complications, some of which will be presented in other documents in this series. The most important of these complications are kidney involvement (Genitourinary Diseases); involvement of the brain or nerves, referred to as neuropsychiatric lupus; and heart involvement (Cardiovascular Diseases). Similar to RA, the disease is usually waxing and waning in nature, sometimes with progressive damage to vital organs over time. Two health states are presented for SLE to capture periods of acute exacerbations (flare-ups), and periods of chronically active disease where a low level of symptoms is present on an ongoing basis, but the disease is not in a flare-up. The functional limitations associated with progressive damage depend on the organ(s) affected and the severity of the damage, therefore, this health state will not be described because it is highly variable. Periods of remission are also possible with SLE (although rare); during this stage, the disease is almost or completely inactive and thus will also not be described here.
Fibromyalgia is a chronic condition of the soft tissues characterized by widespread pain and fatigue. It affects approximately 3% of Canadians,4,5 with females comprising the majority of cases. Fibromyalgia is a fairly recent term and the condition is not classified in the ICD-9 coding. However, it was previously referred to as non-articular rheumatism or fibrositis,6 and is thus classified under rheumatism, unspecified and fibrositis (ICD-9 729.0). Fibromyalgia is classified in the ICD-10 under musculoskeletal diseases, soft tissue disorders, rheumatism, unspecified (M79.0).7
Osteoporosis is a disease of the musculoskeletal system (ICD-9 code: 733.0) in which the bone deteriorates (i.e., becomes thin and brittle) over time, causing the bone to become highly susceptible to fracture. Approximately 1 million Canadians suffer from the disease, and 80% are women.8 A health state for osteoporosis is not included in this chapter because it is generally asymptomatic until a fracture occurs. Fractures are included in another document in this series (Injuries).