The ends of the bones in the knee are covered with “cartilage” called the “Articular cartilage” this is different to the small horse shoe shaped catilages (meniscus) which are in between the bone ends.
The green shaded bits are articular cartilage
Arthrits is basically wearing out of this articular cartilage. Commonly due to the normal ageing process (osteo arthritis), due to injury (post-traumatic arthritis), inflammation in the knee (inflammatory arthritis such as Rheumatoid arthritis), metabolic conditions such as gout (excess uric acid in the blood) and many other less common conditions.
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