So, if you have arthritis and a meniscus condition in your knee, you can only receive a rating for one of the two conditions, whichever gives the higher rating. So, if your arthritis gives a higher rating than the meniscus condition, then it is rated, and the other is ignored. Only one rating per joint.
Drugs are chemicals that can alter the way the body works. There are different types of drugs, and these have different effects on the body. Tobacco and alcohol are legal recreational drugs which have potentially serious effects on the body. Illegal drugs are classified on a scale from Class A - the most dangerous - to Class C - the least dangerous.
Important note: All of these drugs are dangerous, but none of these drugs is The Devil in Powdered Form. Every one of these drugs has been used with no visible detrimental effect by some lucky people, but every one of these drugs could also destroy your life.