Knee osteoarthritis is a progressive and lifelong joint disease caused by the deterioration and loss of function of the cartilage that covers the ends of the bones forming the knee joint. It is one of the most common knee conditions and typically affects individuals over the age of 50. As the smooth, shock-absorbing cartilage surface breaks down, symptoms such as knee pain, stiffness, swelling, and limited range of motion begin to appear. Daily activities like climbing stairs, standing for long periods, or getting up from a seated position can become increasingly difficult. While non-surgical treatments can help manage symptoms in the early stages, knee replacement surgery becomes inevitable in advanced cases.<\/p>\n\n\n\n
Knee osteoarthritis is a degenerative joint disease that develops when the cartilage covering the ends of the bones in the knee loses its structural integrity over time. As the cartilage thins, bones begin to rub against each other during movement, leading to pain, swelling, restricted mobility, and a noticeable decline in quality of life.<\/p>\n\n\n\n
Although both knees can be affected, one knee may deteriorate faster or present with more severe symptoms than the other. The progression of the disease varies among individuals\u2014while it may develop slowly over the years in some, others may experience rapid deterioration.<\/p>\n\n\n\n
Knee osteoarthritis (OA) is not merely a mechanical issue caused by aging or overuse. Research now shows that this condition affects all structures of the knee joint \u2014 especially the cartilage, synovial membrane, joint capsule, and underlying bone \u2014 through a slow and complex biological process.<\/p>\n\n\n\n
Healthy cartilage is a smooth and flexible tissue that enables bones in the knee to glide over one another without friction. In the early stages of osteoarthritis, the water content in the cartilage increases<\/a><\/strong>, and the structure of proteoglycans (components of the cartilage matrix) begins to change and eventually degrade. Collagen fibers lose their organized structure, and small cracks appear on the surface of the cartilage. Over time, the cartilage softens, thins, and erodes.<\/p>\n\n\n\n The degenerative process is not limited to cartilage damage. Inflammation of the synovial membrane (synovitis) is a known feature of osteoarthritis:<\/p>\n\n\n\n As the cartilage deteriorates, the underlying bone attempts to adapt by reshaping itself:<\/p>\n\n\n\n Although these changes may seem like the body\u2019s attempt to repair the joint, they often worsen pain and further restrict movement.<\/p>\n\n\n\n In osteoarthritis, certain cells begin to overproduce enzymes \u2014 such as matrix metalloproteinases (MMPs) and aggrecanases \u2014 that break down cartilage. Under normal conditions, the body regulates these enzymes, but in osteoarthritis, this balance is disrupted, accelerating cartilage destruction. Inflammatory cytokines such as IL-1, IL-6, and TNF-alpha play a major role in driving this process.<\/p>\n\n\n\n Genetics may also contribute to the development and severity of knee osteoarthritis. Individuals with a family history of osteoarthritis may carry specific genetic traits that cause the disease to manifest earlier and progress more severely. Variants in genes such as the vitamin D receptor, estrogen receptor, matrilin-3, BMP-2, and BMP-5 have been implicated.<\/p>\n\n\n\n Knee osteoarthritis does not develop at the same pace or severity in every individual. Certain risk factors can make some people more prone to developing osteoarthritis. While these factors may not directly cause the disease, they can accelerate cartilage degeneration and lead to symptoms appearing at an earlier age.<\/p>\n\n\n\n The main risk factors include:<\/strong><\/p>\n\n\n\n There is a widespread belief that running wears out the knees. However, scientific studies suggest otherwise. Research conducted on athletes who have been running over 30 km per week and completing at least one marathon per year shows that their risk of requiring knee replacement is lower than that of the general population.<\/p>\n\n\n\n In fact, when done with proper technique, running can help protect the knee joint rather than damage it. For individuals with a healthy body weight and no previous serious knee injuries, regular running enhances cartilage nutrition and joint fluid circulation, promoting overall knee health.<\/p>\n\n\n\n That said, running without proper footwear, technique, or on unsuitable surfaces may lead to other issues. Still, brisk walking or controlled running several times a week can play a crucial role in preventing knee osteoarthritis.<\/p>\n\n\n\n Knee osteoarthritis can develop at a young age due to several contributing factors:<\/p>\n\n\n\n Early-onset knee osteoarthritis can significantly affect quality of life due to its progressive nature. Therefore, people at risk should adopt a joint-friendly lifestyle and take preventive measures as early as possible.<\/p>\n\n\n\n The severity of knee osteoarthritis is commonly classified from grade 0 to grade 4 based on X-ray findings. This grading system helps determine how advanced the disease is and guides appropriate treatment options. The most widely used classification is the Kellgren-Lawrence grading system<\/strong>.<\/p>\n\n\n\n Knee osteoarthritis is a slowly progressive disease, and its symptoms often emerge gradually over time. Initially mild, these complaints can eventually interfere with daily activities as the condition worsens. The symptoms may vary depending on the degree of cartilage loss, inflammation inside the joint, and the amount of weight placed on the knee.<\/p>\n\n\n\nInflammation of the Synovial Membrane<\/strong><\/h3>\n\n\n\n
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Changes in the Bone<\/strong><\/h3>\n\n\n\n
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Cellular and Biochemical Mechanisms<\/strong><\/h3>\n\n\n\n
Genetic Predisposition<\/strong><\/h3>\n\n\n\n
Risk Factors for Knee Osteoarthritis<\/strong><\/h2>\n\n\n\n
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Does Running Cause Knee Osteoarthritis?<\/strong><\/h2>\n\n\n\n
What Causes Early-Onset Knee Osteoarthritis?<\/strong><\/h2>\n\n\n\n
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Stages of Knee Osteoarthritis (Grading System)<\/strong><\/h2>\n\n\n\n
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What Are the Symptoms of Knee Osteoarthritis?<\/strong><\/h2>\n\n\n\n