Chapter 28 Anna E. Litwic and Elaine M. Dennison MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, Southampton, UK Globally, all musculoskeletal disorders combined account for over 20% of the total years lived with disability, second only to mental and behavioural problems. Each year, 20% of the UK general population consult a GP with a musculoskeletal problem. The most common rheumatic diseases are osteoarthritis (OA) and gout (Figure 28.1). These diseases become more prevalent with age; since it has been estimated that the proportion of over‐65 s in the population will increase three‐fold in the next 30 years, this demographic change will significantly increase the burden on healthcare systems from musculoskeletal disorders. Figure 28.1 Number of patients consulting in 1 year by condition in a practice of 10 000 Osteoarthritis (OA) is the most common form of arthritis and a leading cause of disability. OA may develop in any joint, but most commonly affects the knees, hips, hands, facet joints and feet. The prevalence of OA varies greatly depending on the definition used (radiological, clinical or self‐reported), age, sex and geographical area studied. OA of the hips and knees tends to cause the greatest burden to the population as pain and stiffness in these large weight‐bearing joints often lead to significant disability requiring surgical intervention. Psychological distress is more frequently experienced by patients with OA compared to patients with other chronic diseases. A radiographic case definition of OA results in the highest reported prevalence. Interestingly, individuals with early clinical OA may be free of radiographic changes and, conversely, those with severe radiographic changes may be entirely asymptomatic, although there is a correlation between the severity of radiographic disease and symptoms. The incidence of hand, hip and knee OA increases with age, and women have higher rates than men, especially after the age of 50 years. It is estimated that each year, over 2 million people in the UK visit their GP with OA symptoms. There are a number of systemic and local risk factors associated with OA (Box 28.1). Genetic factors are important, and OA in some families displays classic mendelian inheritance. The heritability of cartilage volume, as a marker of degeneration, has been estimated at over 70%. Congenital joint deformities may increase the stress on the cartilage and contribute to OA development. The increase of obesity in the population is one of the major factors associated with both the development of knee OA and progression of the disease; having a high body mass index has been associated with up to nine‐fold increased risk of knee OA. Joint injury can also increase the risk of OA. This may be due to direct cartilage damage or a result of increased stress on the cartilage due to the injury. Workers in certain occupations are at increased risk, for example jobs that require excessive knee bending and farming. Recent studies have shown that a low vitamin D intake can increase the risk of OA, and a high vitamin C intake may reduce the risk. The majority of chronic pain experienced by older adults is musculoskeletal in origin. The severity of symptoms and their impact on the patient’s life vary greatly. The pain can be generalized or affect one region. The most commonly reported localized pain is sited in the lower back, knee, neck, foot and shoulder (Figure 28.2). Figure 28.2 Number of people consulting for problems in selected regions by age in a practice of 10 000 Low back pain (LBP) is a symptom, not a disease. Despite several potential causes for LBP (Box 28.2), it is often difficult to establish a single underlying cause. Every year, around 7% of the adult UK population present in general practice with LBP. Back pain tends to be episodic and the majority of episodes settle within 6 weeks. However, back pain is also recurrent and back pain in the past is one of the strongest predictors for back pain in the future. The lifetime incidence of back pain ranges between 58% and 84%. A number of studies have suggested that fewer than 20% of back pain episodes are brought to medical attention. LBP is generally more common in women and the prevalence increases with age. A number of risk factors are implicated with LBP, including poor posture, occupation, poor job satisfaction, smoking, obesity, previous LBP episode and lower social class (Box 28.3). The prevalence of back disability is thought to be increasing faster than any other form of disability. According to the Labour Force Survey, the prevalence of work‐related musculoskeletal disorders mainly affecting the back was reported to be 800 per 100 000 in 2007, and estimated to result in the loss of 4.1 million working days.
Epidemiology of the Rheumatic Diseases
Osteoarthritis
Musculoskeletal pain
Low back pain
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