What Knee Osteoarthritis Is and Its Main Risk Factors

Anthony describes knee osteoarthritis as one of the most common chronic diseases, with symptomatic osteoarthritis in 9.6% of men and 18% of women over 60 worldwide. Using the 2015 OARSI definition and a systems model, cartilage health depends on biology, functional mechanics and joint structure. A risk factor pushes the joint out of homeostasis and, if sustained, leads to cartilage degradation and clinical disease. Severity is graded on the Kellgren-Lawrence scale. Risk factors include age, obesity, previous knee injury, female sex, abnormal joint loading, quadriceps weakness, malalignment, genetics and occupational kneeling or lifting. About half of people aged 45 to 75 do not develop clinical osteoarthritis, so age alone does not explain it. Obesity adds a metabolic, inflammatory effect on top of load. About half of people with ligament or meniscal injuries have osteoarthritis 10 to 20 years later, and initial meniscal resection is a strong risk factor. Elite soccer, elite long-distance running, weightlifting and wrestling show higher prevalence, likely tied partly to injury.