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Prevalence of osteoarthritis of the knee in a random population sample of people aged 40 and older

Traditionally, the concept of osteoarthritis has been focused on articular cartilage degradation. However, in recent years, the concept of the disease has changed, and it involves the rest of the anatomical structures that make up the joint: subchondral bone, ligaments, meniscus, joint capsule, synovial membrane and periarticular muscle, with the joint being regarded as a neuromusculoskeletal unit.1-4 Tissue injury mechanisms include mechanical and biological factors; in addition, osteoarthritis is a highly metabolically active disease.5-7 Osteoarthritis is the osteoarticular disease with the highest prevalence in the entire world. In industrialized countries, 80 % of the population older than 65 years suffer osteoarthritis8 and knee or hip involvement is the most common cause of ambulation disability in the elderly.9 In Spain, the symptomatic prevalence of osteoarthritis of the knee in people older than 20 years is 10.2 % and that of symptomatic osteoarthritis of the hands is 6.2 %.10 There are numerous epidemiological studies on the prevalence of osteoarthritis in different populations, but their results are not easy to be generalized and compared due to the variability in the definition of the disease (clinical or radiographic criteria), selection biases (participants’ age and gender), selected joints, difficulty in establishing early symptoms of the disease and diversity in population pain threshold.11-13 Osteoarthritis clinical data usually appear after 40 years of age, with gradual onset and slow evolution, with differences according to sites and individuals. Pain is the cardinal symptom (of mechanical characteristics). Other signs and symptoms include joint stiffness (of short duration), joint deformity, crepitus, weakness or instability.14-16 Abstract