Total knee replacement may be done on people, usually over 55, whose knees have been damaged by arthritis, trauma, or other destructive diseases of the joint resulting in severe limiting knee pain and significant stiffness, instability (constant giving way) and deformity (lock-knees or bowlegs) of the knee.
The Mexican government has a Federal District, which houses the federal government. The Federal District is a physical place and a territory, bordering Mexico City, which is the country's capital city. This is not counted as one of the states, and is much like the United States' District of Columbia.
This concept, which arises from the Mexican Revolution, is known as a free municipality. In total there are 2438 municipalities in Mexico, the state with the highest number of municipalities is Oaxaca, with 570, and the state with the lowest number is Baja California, with only 5.