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Knee osteoarthritis is a condition where cartilage in the knee degenerates, or breaks down, which can lead to inflammation, pain, and swelling in the knee joint.
The knee is the largest joint in the body. It is the point where the femur, or thigh bone, meets the tibia, or shin bone, as well as the fibula, which is a smaller bone that runs beside the tibia.
Articular cartilage covers the condyle, the curved end of the femur where it meets the meniscus, a rubbery segment of cartilage that covers the tibia and acts as a shock absorber.
Articular cartilage also lines the underside of the patella, or kneecap, which floats above the spot where the other three leg bones meet.
In a healthy knee, the presence of cartilage allows the leg bones and the patella to glide smoothly during the joint’s hinge-like movements.
But with knee osteoarthritis, this cartilage begins to degenerate, either due to the wear and tear of aging, prior traumatic injury, or both.
The first sign of knee osteoarthritis is often aching pain, swelling, or stiffness in the knee, which indicates the knee’s cartilage is inflamed.
The inflamed knee cartilage begins to thin and may even disappear completely, causing direct friction of the knee bones against one another.
This bone-on-bone friction can lead to the development of osteophytes, or bone spurs, in the knee joint, which can cause pain if they increase joint friction.
As knee osteoarthritis progresses, patients can lose some or all of the knee’s range of motion, or its ability to bear the body's weight.