Osteoarthritis (OA) is a common joint condition affecting millions globally. It develops when the protective cartilage, cushioning the ends of bones, gradually wears away or becomes damaged. This degradation can lead to bones rubbing directly, causing discomfort and limiting movement. Healthcare professionals sometimes refer to it as degenerative joint disease due to this progressive breakdown of joint tissues.
Global and Regional Scope
Osteoarthritis is the most prevalent form of arthritis, affecting a large portion of the global population. In 2020, approximately 595 million people globally had OA, accounting for 7.6% of the worldwide population. This reflects a 132% increase in cases since 1990, highlighting a growing public health challenge. By 2050, knee OA cases could increase by nearly 75%, hand OA by almost 49%, and hip OA by about 79%.
Osteoarthritis prevalence shows regional variations globally. In 2020, age-standardized rates exceeded 5.5% in all regions. High-income Asia Pacific and North America recorded the highest age-standardized prevalence, with rates around 8,633 and 8,432 per 100,000 people, respectively. Conversely, Southeast Asia, Eastern and Central sub-Saharan Africa reported lower rates, ranging from 5,677 to 5,946 per 100,000. The knee is the most commonly affected joint worldwide.
Demographic Variations
OA prevalence varies considerably across different demographic groups, with age being a prominent factor. It rises steadily with advancing age, and symptoms often appear more frequently in individuals over 50. For instance, in 2020, the prevalence for those aged 70 and older was 38,419 per 100,000, significantly higher than the 23,237 per 100,000 for those aged 50-69. While often associated with aging, OA can also affect younger individuals, particularly those with a history of joint injury.
Sex differences are evident in OA prevalence, with women generally experiencing higher rates than men. In 2020, global age-standardized prevalence for females was 8,059 per 100,000, compared to 5,780 per 100,000 for males. This disparity becomes more pronounced after age 50, with increased knee OA incidence in women after menopause, suggesting physiological changes. Women also tend to experience more severe knee and hand OA compared to men.
Variations in OA prevalence are observed among ethnic and racial groups. In the U.S., African Americans show a higher likelihood of developing symptomatic and radiological knee OA, often with more severe features, compared to non-Hispanic whites. They also report more pronounced pain and disability due to OA. Factors such as genetics, certain health conditions like diabetes and hypertension, and social determinants of health may contribute to these differences.
Factors Influencing Prevalence
Several factors contribute to the widespread occurrence of OA. Obesity is a modifiable risk factor, as excess body weight places stress on weight-bearing joints like the hips and knees. Beyond mechanical stress, fat cells can promote inflammation, contributing to joint damage. High body-mass index (BMI) contributed to over 20% of OA cases in 2020.
Previous joint injuries (e.g., fractures, sprains, ligament or cartilage tears) substantially increase the risk of developing OA. Even minor traumas or repetitive stress from sports or occupational activities can lead to the condition. For example, knee trauma elevates the risk of knee OA by nearly four times. Genetic predisposition also plays a role, with inherited factors increasing susceptibility.
Certain pre-existing joint diseases like rheumatoid arthritis or gout can contribute to OA by damaging joint cartilage. Additionally, metabolic conditions like diabetes have been linked to an increased OA risk. These factors, alongside age and sex, collectively influence global prevalence patterns.
Societal and Economic Impact
High OA prevalence imposes a substantial burden on healthcare systems and affected individuals. Direct costs include treatment, medications, joint replacement surgeries, and long-term care. For example, hip and knee replacement surgeries can cost hundreds of millions of pounds annually in some countries. Increasing OA prevalence, driven by aging populations and rising obesity, is expected to escalate healthcare expenditures.
Beyond direct medical costs, OA impacts individuals’ quality of life. Chronic pain, stiffness, and reduced mobility interfere with daily activities, leading to disability and a decreased sense of well-being. People with moderate or severe OA often experience limitations in meaningful activities and may suffer psychological distress.
Economically, the widespread occurrence of OA results in considerable indirect costs. These include lost productivity from missed workdays, reduced workforce participation, and the need for professional care. In some regions, economic production lost due to OA-related work absences can amount to billions of pounds annually. The societal and economic consequences underscore the broader implications of this prevalent joint condition.