Stephen Hawking: 'There is no heaven; it's a fairy story'. In an exclusive interview with the Guardian, the cosmologist shares his thoughts on death, M-theory, human purpose and our chance existence. , science correspondent. Sunday 15 May 2011 17.00 EDT First published on Sunday 15 May 2011 17.00 EDT.
Both the growth of a tumor and the repair of a scrape on the knee are similar because they involve a mass amount of blood cells in a particular area. A growth of a tumor is a huge mass of cells that form together an cause it. And like the forming tumor, when you get a scrape on your knee blood cells are clumped together forming a large mass of blood also. They are different because there isn't an opening to a tumor allowing blood cells to flow out. When there is a scrape on your knee, there is an opening/cut, allowing blood cells to flow out properly.
The articular cartilage (lining of the knee joint) can be damaged by either an acute injury or repetitive wear and tear. Articular cartilage has very poor potential to repair itself once it has been damaged. There are a number of surgical options available to treat areas of cartilage damage. The most commonly carried out procedure is a chondroplasty. This term covers a number of simple techniques aimed at reshaping and smoothing-off of any areas of damage to the articular cartilage. Chondroplasty involves removing loose flaps of cartilage (this can cause a sensation of catching and pain in the knee). Micro-instruments are inserted into the knee and used to take away any loose fragments of articular cartilage and stabilise the remaining tissue.